Chat server
You are encouraged to solve this task according to the task description, using any language you may know.
- Task
Write a server for a minimal text based chat.
People should be able to connect via ‘telnet’, sign on with a nickname, and type messages which will then be seen by all other connected users. Arrivals and departures of chat members should generate appropriate notification messages.
Ada
<lang Ada>with Ada.Containers.Vectors; with Ada.Command_Line; use Ada.Command_Line; with Ada.Exceptions; use Ada.Exceptions; with Ada.Text_IO; use Ada.Text_IO; with Ada.Strings.Unbounded; use Ada.Strings.Unbounded; with Sockets; use Sockets;
procedure Chat_Server is
package Client_Vectors is new Ada.Containers.Vectors
(Element_Type => Socket_FD, Index_Type => Positive);
All_Clients : Client_Vectors.Vector;
procedure Write (S : String) is
procedure Output (Position : Client_Vectors.Cursor) is
Sock : Socket_FD := Client_Vectors.Element (Position);
begin
Put_Line (Sock, S);
end Output;
begin
All_Clients.Iterate (Output'Access);
end Write;
task type Client_Task is
entry Start (FD : Socket_FD);
end Client_Task;
task body Client_Task is
Sock : Socket_FD;
Sock_ID : Positive;
Name : Unbounded_String;
begin
select
accept Start (FD : Socket_FD) do
Sock := FD;
end Start;
or
terminate;
end select;
while Name = Null_Unbounded_String loop
Put (Sock, "Enter Name:");
Name := To_Unbounded_String (Get_Line (Sock));
end loop;
Write (To_String (Name) & " joined.");
All_Clients.Append (Sock);
Sock_ID := All_Clients.Find_Index (Sock);
loop
declare
Input : String := Get_Line (Sock);
begin
Write (To_String (Name) & ": " & Input);
end;
end loop;
exception
when Connection_Closed =>
Put_Line ("Connection closed");
Shutdown (Sock, Both);
All_Clients.Delete (Sock_ID);
Write (To_String (Name) & " left.");
end Client_Task;
Accepting_Socket : Socket_FD; Incoming_Socket : Socket_FD;
type Client_Access is access Client_Task; Dummy : Client_Access;
begin
if Argument_Count /= 1 then
Raise_Exception (Constraint_Error'Identity,
"Usage: " & Command_Name & " port");
end if;
Socket (Accepting_Socket, PF_INET, SOCK_STREAM);
Setsockopt (Accepting_Socket, SOL_SOCKET, SO_REUSEADDR, 1);
Bind (Accepting_Socket, Positive'Value (Argument (1)));
Listen (Accepting_Socket);
loop
Put_Line ("Waiting for new connection");
Accept_Socket (Accepting_Socket, Incoming_Socket);
Put_Line ("New connection acknowledged");
Dummy := new Client_Task;
Dummy.Start (Incoming_Socket);
end loop;
end Chat_Server;</lang>
C
C has no built-in networking functions, but the POSIX library does provide some low-level networking functions. The functions of interest relating to sockets include bind, listen, select, accept, read, write and close.
The example below was compiled on Cygwin, and accepts PuTTY connections under the RAW protocol.
A glitch occurs if a connection is made using the Telnet protocol - user names are preceded by garbled text.
<lang c>#include <stdio.h>
- include <stdlib.h>
- include <sys/socket.h>
- include <sys/select.h>
- include <netinet/in.h>
- include <netinet/ip.h>
int tsocket; struct sockaddr_in tsockinfo; fd_set status, current; void ClientText(int handle, char *buf, int buf_len);
struct client {
char buffer[4096]; int pos; char name[32];
} *connections[FD_SETSIZE];
void AddConnection(int handle) {
connections[handle] = malloc(sizeof(struct client)); connections[handle]->buffer[0] = '\0'; connections[handle]->pos = 0; connections[handle]->name[0] = '\0';
}
void CloseConnection(int handle) {
char buf[512]; int j;
FD_CLR(handle, &status);
if (connections[handle]->name[0])
{
sprintf(buf, "* Disconnected: %s\r\n", connections[handle]->name);
for (j = 0; j < FD_SETSIZE; j++)
{
if (handle != j && j != tsocket && FD_ISSET(j, &status))
{
if (write(j, buf, strlen(buf)) < 0)
{
CloseConnection(j);
}
}
}
} else
{
printf ("-- Connection %d disconnected\n", handle);
}
if (connections[handle])
{
free(connections[handle]);
}
close(handle);
}
void strip(char *buf) {
char *x;
x = strchr(buf, '\n');
if (x) { *x='\0'; }
x = strchr(buf, '\r');
if (x) { *x='\0'; }
}
int RelayText(int handle) {
char *begin, *end;
int ret = 0;
begin = connections[handle]->buffer;
if (connections[handle]->pos == 4000)
{
if (begin[3999] != '\n')
begin[4000] = '\0';
else {
begin[4000] = '\n';
begin[4001] = '\0';
}
} else {
begin[connections[handle]->pos] = '\0';
}
end = strchr(begin, '\n');
while (end != NULL)
{
char output[8000];
output[0] = '\0';
if (!connections[handle]->name[0])
{
strncpy(connections[handle]->name, begin, 31);
connections[handle]->name[31] = '\0';
strip(connections[handle]->name);
sprintf(output, "* Connected: %s\r\n", connections[handle]->name);
ret = 1;
} else
{
sprintf(output, "%s: %.*s\r\n", connections[handle]->name,
end-begin, begin);
ret = 1;
}
if (output[0])
{
int j;
for (j = 0; j < FD_SETSIZE; j++)
{
if (handle != j && j != tsocket && FD_ISSET(j, &status))
{
if (write(j, output, strlen(output)) < 0)
{
CloseConnection(j);
}
}
}
}
begin = end+1;
end = strchr(begin, '\n');
}
strcpy(connections[handle]->buffer, begin);
connections[handle]->pos -= begin - connections[handle]->buffer;
return ret;
}
void ClientText(int handle, char *buf, int buf_len) {
int i, j;
if (!connections[handle])
return;
j = connections[handle]->pos;
for (i = 0; i < buf_len; ++i, ++j)
{
connections[handle]->buffer[j] = buf[i];
if (j == 4000)
{
while (RelayText(handle));
j = connections[handle]->pos;
}
}
connections[handle]->pos = j;
while (RelayText(handle));
}
int ChatLoop()
{
int i, j; FD_ZERO(&status);
FD_SET(tsocket, &status); FD_SET(0, &status);
while(1)
{
current = status;
if (select(FD_SETSIZE, ¤t, NULL, NULL, NULL)==-1)
{
perror("Select");
return 0;
}
for (i = 0; i < FD_SETSIZE; ++i)
{
if (FD_ISSET(i, ¤t))
{
if (i == tsocket)
{
struct sockaddr_in cliinfo;
socklen_t addrlen = sizeof(cliinfo);
int handle;
handle = accept(tsocket, &cliinfo, &addrlen);
if (handle == -1)
{
perror ("Couldn't accept connection");
} else if (handle > FD_SETSIZE)
{
printf ("Unable to accept new connection.\n");
close(handle);
}
else
{
if (write(handle, "Enter name: ", 12) >= 0)
{
printf("-- New connection %d from %s:%hu\n",
handle,
inet_ntoa (cliinfo.sin_addr),
ntohs(cliinfo.sin_port));
FD_SET(handle, &status);
AddConnection(handle);
}
}
} /* Read data, relay to others. */
else
{
char buf[512];
int b;
b = read(i, buf, 500);
if (b <= 0)
{
CloseConnection(i);
}
else
{
ClientText(i, buf, b);
}
}
}
}
} /* While 1 */
}
int main (int argc, char*argv[]) {
tsocket = socket(PF_INET, SOCK_STREAM, 0);
tsockinfo.sin_family = AF_INET;
tsockinfo.sin_port = htons(7070);
if (argc > 1)
{
tsockinfo.sin_port = htons(atoi(argv[1]));
}
tsockinfo.sin_addr.s_addr = htonl(INADDR_ANY);
printf ("Socket %d on port %hu\n", tsocket, ntohs(tsockinfo.sin_port));
if (bind(tsocket, &tsockinfo, sizeof(tsockinfo)) == -1)
{
perror("Couldn't bind socket");
return -1;
}
if (listen(tsocket, 10) == -1)
{
perror("Couldn't listen to port");
}
ChatLoop();
return 0;
}</lang>
CoffeeScript
This is ported from the JavaScript version. The tool js2coffee got me a mostly working version, and then I manually converted JS-style classes to CS "classic-style class" syntax.
<lang coffeescript> net = require("net") sys = require("sys") EventEmitter = require("events").EventEmitter
isNicknameLegal = (nickname) ->
return false unless nickname.replace(/[A-Za-z0-9]*/, "") is "" for used_nick of @chatters return false if used_nick is nickname true
class ChatServer
constructor: ->
@chatters = {}
@server = net.createServer @handleConnection
@server.listen 1212, "localhost"
handleConnection: (connection) => console.log "Incoming connection from " + connection.remoteAddress connection.setEncoding "utf8" chatter = new Chatter(connection, this) chatter.on "chat", @handleChat chatter.on "join", @handleJoin chatter.on "leave", @handleLeave
handleChat: (chatter, message) => @sendToEveryChatterExcept chatter, chatter.nickname + ": " + message
handleJoin: (chatter) => console.log chatter.nickname + " has joined the chat." @sendToEveryChatter chatter.nickname + " has joined the chat." @addChatter chatter
handleLeave: (chatter) => console.log chatter.nickname + " has left the chat." @removeChatter chatter @sendToEveryChatter chatter.nickname + " has left the chat."
addChatter: (chatter) => @chatters[chatter.nickname] = chatter
removeChatter: (chatter) => delete @chatters[chatter.nickname]
sendToEveryChatter: (data) =>
for nickname of @chatters
@chatters[nickname].send data
sendToEveryChatterExcept: (chatter, data) =>
for nickname of @chatters
@chatters[nickname].send data unless nickname is chatter.nickname
class Chatter extends EventEmitter
constructor: (socket, server) -> EventEmitter.call this @socket = socket @server = server @nickname = "" @lineBuffer = new SocketLineBuffer(socket) @lineBuffer.on "line", @handleNickname @socket.on "close", @handleDisconnect @send "Welcome! What is your nickname?"
handleNickname: (nickname) =>
if isNicknameLegal(nickname)
@nickname = nickname
@lineBuffer.removeAllListeners "line"
@lineBuffer.on "line", @handleChat
@send "Welcome to the chat, " + nickname + "!"
@emit "join", this
else
@send "Sorry, but that nickname is not legal or is already in use!"
@send "What is your nickname?"
handleChat: (line) => @emit "chat", this, line
handleDisconnect: => @emit "leave", this
send: (data) => @socket.write data + "\r\n"
class SocketLineBuffer extends EventEmitter
constructor: (socket) -> EventEmitter.call this @socket = socket @buffer = "" @socket.on "data", @handleData
handleData: (data) => console.log "Handling data", data i = 0
while i < data.length
char = data.charAt(i)
@buffer += char
if char is "\n"
@buffer = @buffer.replace("\r\n", "")
@buffer = @buffer.replace("\n", "")
@emit "line", @buffer
console.log "incoming line: #{@buffer}"
@buffer = ""
i++
server = new ChatServer() </lang>
D
<lang d> import std.getopt; import std.socket; import std.stdio; import std.string;
struct client {
int pos; char[] name; char[] buffer; Socket socket;
}
void broadcast(client[] connections, size_t self, const char[] message) {
writeln(message);
for (size_t i = 0; i < connections.length; i++) {
if (i == self) continue;
connections[i].socket.send(message);
connections[i].socket.send("\r\n");
}
}
bool registerClient(client[] connections, size_t self) {
for (size_t i = 0; i < connections.length; i++) {
if (i == self) continue;
if (icmp(connections[i].name, connections[self].name) == 0) {
return false;
}
}
return true;
}
void main(string[] args) {
ushort port = 4004;
auto helpInformation = getopt
(
args,
"port|p", "The port to listen to chat clients on [default is 4004]", &port
);
if (helpInformation.helpWanted) {
defaultGetoptPrinter("A simple chat server based on a task in rosettacode.", helpInformation.options);
return;
}
auto listener = new TcpSocket();
assert(listener.isAlive);
listener.blocking = false;
listener.bind(new InternetAddress(port));
listener.listen(10);
writeln("Listening on port: ", port);
enum MAX_CONNECTIONS = 60; auto socketSet = new SocketSet(MAX_CONNECTIONS + 1); client[] connections;
while(true) {
socketSet.add(listener);
foreach (con; connections) {
socketSet.add(con.socket);
}
Socket.select(socketSet, null, null);
for (size_t i = 0; i < connections.length; i++) {
if (socketSet.isSet(connections[i].socket)) {
char[1024] buf;
auto datLength = connections[i].socket.receive(buf[]);
if (datLength == Socket.ERROR) {
writeln("Connection error.");
} else if (datLength != 0) {
if (buf[0] == '\n' || buf[0] == '\r') {
if (connections[i].buffer == "/quit") {
connections[i].socket.close();
if (connections[i].name.length > 0) {
writeln("Connection from ", connections[i].name, " closed.");
} else {
writeln("Connection from ", connections[i].socket.remoteAddress(), " closed.");
}
connections[i] = connections[$-1];
connections.length--;
i--;
writeln("\tTotal connections: ", connections.length);
continue;
} else if (connections[i].name.length == 0) {
connections[i].buffer = strip(connections[i].buffer);
if (connections[i].buffer.length > 0) {
connections[i].name = connections[i].buffer;
if (registerClient(connections, i)) {
connections.broadcast(i, "+++ " ~ connections[i].name ~ " arrived +++");
} else {
connections[i].socket.send("Name already registered. Please enter your name: ");
connections[i].name.length = 0;
}
} else {
connections[i].socket.send("A name is required. Please enter your name: ");
}
} else {
connections.broadcast(i, connections[i].name ~ "> " ~ connections[i].buffer);
}
connections[i].buffer.length = 0;
} else {
connections[i].buffer ~= buf[0..datLength];
}
} else {
try {
if (connections[i].name.length > 0) {
writeln("Connection from ", connections[i].name, " closed.");
} else {
writeln("Connection from ", connections[i].socket.remoteAddress(), " closed.");
}
} catch (SocketException) {
writeln("Connection closed.");
}
}
}
}
if (socketSet.isSet(listener)) {
Socket sn = null;
scope(failure) {
writeln("Error accepting");
if (sn) {
sn.close();
}
}
sn = listener.accept();
assert(sn.isAlive);
assert(listener.isAlive);
if (connections.length < MAX_CONNECTIONS) {
client newclient;
writeln("Connection from ", sn.remoteAddress(), " established.");
sn.send("Enter name: ");
newclient.socket = sn;
connections ~= newclient;
writeln("\tTotal connections: ", connections.length);
} else {
writeln("Rejected connection from ", sn.remoteAddress(), "; too many connections.");
sn.close();
assert(!sn.isAlive);
assert(listener.isAlive);
}
}
socketSet.reset(); }
} </lang>
Erlang
<lang erlang> -module(chat).
-export([start/0, start/1]).
-record(client, {name=none, socket=none}).
start() -> start(8080). start(Port) ->
register(server, spawn(fun() -> server() end)),
{ok, LSocket} = gen_tcp:listen(Port, [binary, {packet, 0}, {active, false}, {reuseaddr, true}]),
accept(LSocket).
% main loop for message dispatcher server() -> server([]). server(Clients) ->
receive
{join, Client=#client{name = Name, socket = Socket}} ->
self() ! {say, Socket, "has joined." ++ [10, 13]},
server(Clients ++ [Client]);
{leave, Socket} ->
{value, #client{name = Name}, List} = lists:keytake(Socket, 3, Clients),
self() ! {say, none, Message = "has left."},
server(List);
{say, Socket, Data} ->
{value, #client{name = From}, List} = lists:keytake(Socket, 3, Clients),
Message = From ++ " : " ++ Data,
lists:map(fun(#client{socket = S}) ->
gen_tcp:send(S, Message)
end, List)
end,
server(Clients).
% accepts connections then spawns the client handler accept(LSocket) ->
{ok, Socket} = gen_tcp:accept(LSocket),
spawn(fun() -> connecting(Socket) end),
accept(LSocket).
% when client is first connect send prompt for user name connecting(Socket) ->
gen_tcp:send(Socket, "What is your name? "),
case listen(Socket) of
{ok, N} ->
Name = binary_to_list(N),
server ! {join, #client{name = lists:sublist(Name, 1, length(Name) - 2), socket = Socket} },
client(Socket);
_ -> ok
end.
% main client loop that listens for data client(Socket) ->
case listen(Socket) of
{ok, Data} ->
server ! {say, Socket, binary_to_list(Data)},
client(Socket);
_ -> server ! {leave, Socket}
end.
% utility function that listens for data on a socket listen(Socket) ->
case gen_tcp:recv(Socket, 0) of
Response -> Response
end.
</lang>
Go
This example uses the Go idiom of Do not communicate by sharing memory; instead, share memory by communicating; there are no explicit locks used, instead Go channels are used to safely synchronize where required.
A similar exercise of a chat roulette (different in that messages only have to be written to a single partner rather than broadcast, this simplifies the code greatly) was the topic of a 2012 Go Talk.
This example handles the case of one specific client "falling behind" by relying on the underlying TCP stack to do a reasonable job of buffering. Once that buffer fills, a write to the that client's connection will time out and the connection will dropped. Other minor improvements would include enabling TCP keep alives, handling temporary errors from accept, and better logging. Not ideal, but it should be good enough for this example.
<lang go>package main
import ( "bufio" "flag" "fmt" "log" "net" "strings" "time" )
func main() { log.SetPrefix("chat: ") addr := flag.String("addr", "localhost:4000", "listen address") flag.Parse() log.Fatal(ListenAndServe(*addr)) }
// A Server represents a chat server that accepts incoming connections. type Server struct { add chan *conn // To add a connection rem chan string // To remove a connection by name msg chan string // To send a message to all connections stop chan bool // To stop early }
// ListenAndServe listens on the TCP network address addr for // new chat client connections. func ListenAndServe(addr string) error { ln, err := net.Listen("tcp", addr) if err != nil { return err } log.Println("Listening for connections on", addr) defer ln.Close() s := &Server{ add: make(chan *conn), rem: make(chan string), msg: make(chan string), stop: make(chan bool), } go s.handleConns() for { // TODO use AcceptTCP() so that we can get a TCPConn on which // we can call SetKeepAlive() and SetKeepAlivePeriod() rwc, err := ln.Accept() if err != nil { // TODO Could handle err.(net.Error).Temporary() // here by adding a backoff delay. close(s.stop) return err } log.Println("New connection from", rwc.RemoteAddr()) go newConn(s, rwc).welcome() } }
// handleConns is run as a go routine to handle adding and removal of // chat client connections as well as broadcasting messages to them. func (s *Server) handleConns() { // We define the `conns` map here rather than within Server, // and we use local function literals rather than methods to be // extra sure that the only place that touches this map is this // method. In this way we forgo any explicit locking needed as // we're the only go routine that can see or modify this. conns := make(map[string]*conn)
var dropConn func(string) writeAll := func(str string) { log.Printf("Broadcast: %q", str) // TODO handle blocked connections for name, c := range conns { c.SetWriteDeadline(time.Now().Add(500 * time.Millisecond)) _, err := c.Write([]byte(str)) if err != nil { log.Printf("Error writing to %q: %v", name, err) c.Close() delete(conns, name) // Defer all the disconnect messages until after // we've closed all currently problematic conns. defer dropConn(name) } } }
dropConn = func(name string) { if c, ok := conns[name]; ok { log.Printf("Closing connection with %q from %v", name, c.RemoteAddr()) c.Close() delete(conns, name) } else { log.Printf("Dropped connection with %q", name) } str := fmt.Sprintf("--- %q disconnected ---\n", name) writeAll(str) }
defer func() { writeAll("Server stopping!\n") for _, c := range conns { c.Close() } }()
for { select { case c := <-s.add: if _, exists := conns[c.name]; exists { fmt.Fprintf(c, "Name %q is not available\n", c.name) go c.welcome() continue } str := fmt.Sprintf("+++ %q connected +++\n", c.name) writeAll(str) conns[c.name] = c go c.readloop() case str := <-s.msg: writeAll(str) case name := <-s.rem: dropConn(name) case <-s.stop: return } } }
// A conn represents the server side of a single chat connection. // Note we embed the bufio.Reader and net.Conn (and specifically in // that order) so that a conn gets the appropriate methods from each // to be a full io.ReadWriteCloser. type conn struct { *bufio.Reader // buffered input net.Conn // raw connection server *Server // the Server on which the connection arrived name string }
func newConn(s *Server, rwc net.Conn) *conn { return &conn{ Reader: bufio.NewReader(rwc), Conn: rwc, server: s, } }
// welcome requests a name from the client before attempting to add the // named connect to the set handled by the server. func (c *conn) welcome() { var err error for c.name = ""; c.name == ""; { fmt.Fprint(c, "Enter your name: ") c.name, err = c.ReadString('\n') if err != nil { log.Printf("Reading name from %v: %v", c.RemoteAddr(), err) c.Close() return } c.name = strings.TrimSpace(c.name) } // The server will take this *conn and do a final check // on the name, possibly starting c.welcome() again. c.server.add <- c }
// readloop is started as a go routine by the server once the initial // welcome phase has completed successfully. It reads single lines from // the client and passes them to the server for broadcast to all chat // clients (including us). // Once done, we ask the server to remove (and close) our connection. func (c *conn) readloop() { for { msg, err := c.ReadString('\n') if err != nil { break } //msg = strings.TrimSpace(msg) c.server.msg <- c.name + "> " + msg } c.server.rem <- c.name }</lang>
Haskell
<lang haskell>{-# LANGUAGE OverloadedStrings #-} import Network import System.IO import Control.Concurrent import qualified Data.Text as T import Data.Text (Text) import qualified Data.Text.IO as T import qualified Data.Map as M import Data.Map (Map) import Control.Monad.Reader import Control.Monad.Error import Control.Exception import Data.Monoid import Control.Applicative
type ServerApp = ReaderT ThreadData IO data Speaker = Server | Client Text data ThreadData = ThreadData { threadHandle :: Handle
, userTableMV :: MVar (Map Text Handle)}
echoLocal = liftIO . T.putStrLn echoRemote = echoMessage . (">> "<>) echoMessage msg = viewHandle >>= \h -> liftIO $ T.hPutStrLn h msg getRemoteLine = viewHandle >>= liftIO . T.hGetLine putMVarT = (liftIO.) . putMVar takeMVarT = liftIO . takeMVar readMVarT = liftIO . readMVar modifyUserTable fn = viewUsers >>= \mv ->
liftIO $ modifyMVar_ mv (return . fn)
viewHandle = threadHandle <$> ask viewUsers = userTableMV <$> ask
userChat :: ServerApp () userChat = do
name <- addUser
echoLocal name
h <- viewHandle
(flip catchError) (\_ -> removeUser name) $
do echoLocal $ "Accepted " <> name
forever $ getRemoteLine >>= broadcast (Client name)
removeUser :: Text -> ServerApp () removeUser name = do
echoLocal $ "Exception with " <> name <> ", removing from userTable" broadcast Server $ name <> " has left the server" modifyUserTable (M.delete name)
addUser :: ServerApp Text addUser = do
h <- viewHandle
usersMV <- viewUsers
echoRemote "Enter username"
name <- T.filter (/='\r') <$> getRemoteLine
userTable <- takeMVarT usersMV
if name `M.member` userTable
then do echoRemote "Username already exists!"
putMVarT usersMV userTable
addUser
else do putMVarT usersMV (M.insert name h userTable)
broadcast Server $ name <> " has joined the server"
echoRemote "Welcome to the server!\n>> Other users:"
readMVarT usersMV >>=
mapM_ (echoRemote . ("*" <>) . fst)
. filter ((/=name). fst) . M.toList
return name
broadcast :: Speaker -> Text -> ServerApp () broadcast user msg =
viewUsers >>= readMVarT >>= mapM_ (f . snd) . fn . M.toList
where f h = liftIO $ T.hPutStrLn h $ nm <> msg
(fn, nm) = case user of
Server -> (id, ">> ")
Client t -> (filter ((/=t) . fst), t <> "> ")
clientLoop socket users = do
(h, _, _) <- accept socket hSetBuffering h LineBuffering forkIO $ runReaderT userChat (ThreadData h users) clientLoop socket users
main = do
server <- listenOn $ PortNumber 5002 T.putStrLn "Server started" newMVar (M.empty) >>= clientLoop server
</lang>
Icon and Unicon
This is Unicon-specific: <lang unicon>global mlck, nCons, cons
procedure main()
mlck := mutex()
nCons := 0
cons := mutex(set())
while f := open(":12321","na") do {
handle_client(f)
critical mlck: if nCons <= 0 then close(f)
}
end
procedure handle_client(f)
critical mlck: nCons +:= 1
thread {
select(f,1000) & {
writes(f, "Name? ")
nick := (read(f) ? tab(upto('\n\r')))
every write(!cons, nick," has joined.")
insert(cons, f)
while s := read(f) do every write(!cons, nick,": ",s)
}
delete(cons, f)
every write(!cons, nick," has left.")
critical mlck: nCons -:= 1
}
end</lang>
Java
Broadcasting of messages is done by the thread that received the message, so a bad client could potentially disrupt the server. The output buffer is set to 16K in an attempt to alleviate possible symptoms, but I'm not sure if it's effective. Server does not allow duplicate client names, and lists all users online after a successful connection. Client can type "/quit" to quit.
I think ideally, NIO would be used to select() sockets available/ready for I/O, to eliminate the possibility of a bad connection disrupting the server, but this increases the complexity.
<lang java>import java.io.*; import java.net.*; import java.util.*;
public class ChatServer implements Runnable {
private int port = 0;
private List<Client> clients = new ArrayList<Client>();
public ChatServer(int port)
{ this.port = port; }
public void run()
{
try
{
ServerSocket ss = new ServerSocket(port);
while (true)
{
Socket s = ss.accept();
new Thread(new Client(s)).start();
}
}
catch (Exception e)
{ e.printStackTrace(); }
}
private synchronized boolean registerClient(Client client)
{
for (Client otherClient : clients)
if (otherClient.clientName.equalsIgnoreCase(client.clientName))
return false;
clients.add(client);
return true;
}
private void deregisterClient(Client client)
{
boolean wasRegistered = false;
synchronized (this)
{ wasRegistered = clients.remove(client); }
if (wasRegistered)
broadcast(client, "--- " + client.clientName + " left ---");
}
private synchronized String getOnlineListCSV()
{
StringBuilder sb = new StringBuilder();
sb.append(clients.size()).append(" user(s) online: ");
for (int i = 0; i < clients.size(); i++)
sb.append((i > 0) ? ", " : "").append(clients.get(i).clientName);
return sb.toString();
}
private void broadcast(Client fromClient, String msg)
{
// Copy client list (don't want to hold lock while doing IO)
List<Client> clients = null;
synchronized (this)
{ clients = new ArrayList<Client>(this.clients); }
for (Client client : clients)
{
if (client.equals(fromClient))
continue;
try
{ client.write(msg + "\r\n"); }
catch (Exception e)
{ }
}
}
public class Client implements Runnable
{
private Socket socket = null;
private Writer output = null;
private String clientName = null;
public Client(Socket socket)
{
this.socket = socket;
}
public void run()
{
try
{
socket.setSendBufferSize(16384);
socket.setTcpNoDelay(true);
BufferedReader input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
output = new OutputStreamWriter(socket.getOutputStream());
write("Please enter your name: ");
String line = null;
while ((line = input.readLine()) != null)
{
if (clientName == null)
{
line = line.trim();
if (line.isEmpty())
{
write("A name is required. Please enter your name: ");
continue;
}
clientName = line;
if (!registerClient(this))
{
clientName = null;
write("Name already registered. Please enter your name: ");
continue;
}
write(getOnlineListCSV() + "\r\n");
broadcast(this, "+++ " + clientName + " arrived +++");
continue;
}
if (line.equalsIgnoreCase("/quit"))
return;
broadcast(this, clientName + "> " + line);
}
}
catch (Exception e)
{ }
finally
{
deregisterClient(this);
output = null;
try
{ socket.close(); }
catch (Exception e)
{ }
socket = null;
}
}
public void write(String msg) throws IOException
{
output.write(msg);
output.flush();
}
public boolean equals(Client client)
{
return (client != null) && (client instanceof Client) && (clientName != null) && (client.clientName != null) && clientName.equals(client.clientName);
}
}
public static void main(String[] args)
{
int port = 4004;
if (args.length > 0)
port = Integer.parseInt(args[0]);
new ChatServer(port).run();
}
} </lang>
JavaScript
<lang javascript>var net = require("net"); var sys = require("sys"); var EventEmitter = require("events").EventEmitter;
/*******************************************************************************
* ChatServer * * Manages connections, users, and chat messages. ******************************************************************************/
function ChatServer() {
this.chatters = {};
this.server = net.createServer(this.handleConnection.bind(this));
this.server.listen(1212, "localhost");
}
ChatServer.prototype.isNicknameLegal = function(nickname) {
// A nickname may contain letters or numbers only,
// and may only be used once.
if(nickname.replace(/[A-Za-z0-9]*/, ) != "") {
return false
}
for(used_nick in this.chatters) {
if(used_nick == nickname) {
return false;
}
}
return true;
};
ChatServer.prototype.handleConnection = function(connection) {
console.log("Incoming connection from " + connection.remoteAddress);
connection.setEncoding("utf8");
var chatter = new Chatter(connection, this);
chatter.on("chat", this.handleChat.bind(this));
chatter.on("join", this.handleJoin.bind(this));
chatter.on("leave", this.handleLeave.bind(this));
};
ChatServer.prototype.handleChat = function(chatter, message) {
this.sendToEveryChatterExcept(chatter, chatter.nickname + ": " + message);
};
ChatServer.prototype.handleJoin = function(chatter) {
console.log(chatter.nickname + " has joined the chat."); this.sendToEveryChatter(chatter.nickname + " has joined the chat."); this.addChatter(chatter);
};
ChatServer.prototype.handleLeave = function(chatter) {
console.log(chatter.nickname + " has left the chat."); this.removeChatter(chatter); this.sendToEveryChatter(chatter.nickname + " has left the chat.");
};
ChatServer.prototype.addChatter = function(chatter) {
this.chatters[chatter.nickname] = chatter;
};
ChatServer.prototype.removeChatter = function(chatter) {
delete this.chatters[chatter.nickname];
};
ChatServer.prototype.sendToEveryChatter = function(data) {
for(nickname in this.chatters) {
this.chatters[nickname].send(data);
}
};
ChatServer.prototype.sendToEveryChatterExcept = function(chatter, data) {
for(nickname in this.chatters) {
if(nickname != chatter.nickname) {
this.chatters[nickname].send(data);
}
}
};
/*******************************************************************************
* Chatter * * Represents a single user/connection in the chat server. ******************************************************************************/
function Chatter(socket, server) {
EventEmitter.call(this);
this.socket = socket; this.server = server; this.nickname = ""; this.lineBuffer = new SocketLineBuffer(socket);
this.lineBuffer.on("line", this.handleNickname.bind(this));
this.socket.on("close", this.handleDisconnect.bind(this));
this.send("Welcome! What is your nickname?");
};
sys.inherits(Chatter, EventEmitter);
Chatter.prototype.handleNickname = function(nickname) {
if(server.isNicknameLegal(nickname)) {
this.nickname = nickname;
this.lineBuffer.removeAllListeners("line");
this.lineBuffer.on("line", this.handleChat.bind(this));
this.send("Welcome to the chat, " + nickname + "!");
this.emit("join", this);
} else {
this.send("Sorry, but that nickname is not legal or is already in use!");
this.send("What is your nickname?");
}
};
Chatter.prototype.handleChat = function(line) {
this.emit("chat", this, line);
};
Chatter.prototype.handleDisconnect = function() {
this.emit("leave", this);
};
Chatter.prototype.send = function(data) {
this.socket.write(data + "\r\n");
};
/*******************************************************************************
* SocketLineBuffer * * Listens for and buffers incoming data on a socket and emits a 'line' event * whenever a complete line is detected. ******************************************************************************/
function SocketLineBuffer(socket) {
EventEmitter.call(this);
this.socket = socket; this.buffer = "";
this.socket.on("data", this.handleData.bind(this));
};
sys.inherits(SocketLineBuffer, EventEmitter);
SocketLineBuffer.prototype.handleData = function(data) {
for(var i = 0; i < data.length; i++) {
var char = data.charAt(i);
this.buffer += char;
if(char == "\n") {
this.buffer = this.buffer.replace("\r\n", "");
this.buffer = this.buffer.replace("\n", "");
this.emit("line", this.buffer);
this.buffer = "";
}
}
};
// Start the server! server = new ChatServer();</lang>
Julia
Modified to fit the Rosetta Code task from example code for the WebSockets module written by Leah Hanson. To test, start the code and use a browser to connect to localhost:8000. <lang julia> using HttpServer using WebSockets
const connections = Dict{Int,WebSocket}() const usernames = Dict{Int,String}()
function decodeMessage( msg )
String(copy(msg))
end
wsh = WebSocketHandler() do req, client
global connections
@show connections[client.id] = client
println("req is $req")
notifyonline = "Connection from user number $(client.id) is now online."
for (k,v) in connections
if k != client.id
try
write(v, notifyonline)
catch
continue
end
end
end
while true
try
msg = read(client)
catch
telloffline = "User $(usernames[client.id]) disconnected."
println(telloffline, "(The client id was $(client.id).)")
delete!(connections, client.id)
if haskey(usernames, client.id)
delete!(usernames, client.id)
end
for (k,v) in connections
try
write(v, telloffline)
catch
continue
end
end
return
end
msg = decodeMessage(msg)
if startswith(msg, "setusername:")
println("SETTING USERNAME: $msg")
usernames[client.id] = msg[13:end]
notifyusername = "User number $(client.id) chose $(usernames[client.id]) as name handle."
for (k,v) in connections
try
write(v, notifyusername)
catch
println("Caught exception writing to user $k")
continue
end
end
end
if startswith(msg, "say:")
println("EMITTING MESSAGE: $msg")
for (k,v) in connections
if k != client.id
try
write(v, (usernames[client.id] * ": " * msg[5:end]))
catch
println("Caught exception writing to user $k")
continue
end
end
end
end
end
end
onepage = readstring(Pkg.dir("WebSockets","examples","chat-client.html")) httph = HttpHandler() do req::Request, res::Response
Response(onepage)
end
server = Server(httph, wsh) println("Chat server listening on 8000...") run(server,8000) </lang>
Nim
<lang nim>import asyncnet, asyncdispatch
type
Client = tuple socket: AsyncSocket name: string connected: bool
var clients {.threadvar.}: seq[Client]
proc sendOthers(client: Client, line: string) {.async.} =
for c in clients:
if c != client and c.connected:
await c.socket.send(line & "\c\L")
proc processClient(socket: AsyncSocket) {.async.} =
await socket.send("Please enter your name: ")
var client: Client = (socket, await socket.recvLine(), true)
clients.add(client)
asyncCheck client.sendOthers("+++ " & client.name & " arrived +++")
while true:
let line = await client.socket.recvLine()
if line == "":
asyncCheck client.sendOthers("--- " & client.name & " leaves ---")
client.connected = false
return
asyncCheck client.sendOthers(client.name & "> " & line)
proc serve() {.async.} =
clients = @[] var server = newAsyncSocket() server.bindAddr(Port(4004)) server.listen()
while true: let socket = await server.accept() asyncCheck processClient(socket)
asyncCheck serve() runForever()</lang>
Objeck
<lang objeck> use System.IO.Net; use System.Concurrency; use Collection;
bundle Default {
class ChatServer {
@clients : StringMap;
@clients_mutex : ThreadMutex;
New() {
@clients := StringMap->New();
@clients_mutex := ThreadMutex->New("clients_mutex");
}
method : ValidLogin(login_name : String, clients : StringMap) ~ Bool {
if(clients->Has(login_name)) {
return false;
};
return true;
}
function : Main(args : String[]) ~ Nil {
chat_server := ChatServer->New();
chat_server->Run();
}
method : public : Broadcast(message : String, sender : Client) ~ Nil {
client_array : Vector;
critical(@clients_mutex) {
client_array := @clients->GetValues();
};
each(i : client_array) {
client := client_array->Get(i)->As(Client);
if(client <> sender) {
client->Send(message);
};
};
}
method : public : Disconnect(sender : Client) ~ Nil {
send_name := sender->GetName();
Broadcast("+++ {$send_name} has left +++", sender);
critical(@clients_mutex) {
@clients->Remove(sender->GetName());
};
sender->Close();
}
method : public : Run() ~ Nil {
server := TCPSocketServer->New(4661);
if(server->Listen(5)) {
while(true) {
client_sock := server->Accept();
critical(@clients_mutex) {
client_sock->WriteString("login: ");
login_name := client_sock->ReadString();
if(ValidLogin(login_name, @clients)) {
client := Client->New(login_name, client_sock, @self);
@clients->Insert(client->GetName(), client);
client->Execute(Nil);
}
else {
client_sock->WriteString("+++ login in use +++\r\n");
client_sock->Close();
};
};
};
};
server->Close();
}
}
class Client from Thread {
@client_sock : TCPSocket;
@server : ChatServer;
New(login_name : String, client_sock : TCPSocket, server : ChatServer) {
Parent(login_name);
@client_sock := client_sock;
@server := server;
}
method : public : Close() ~ Nil {
@client_sock->Close();
}
method : public : Send(message : String) ~ Nil {
if(@client_sock->IsOpen() & message->Size() > 0) {
@client_sock->WriteString("{$message}\r\n");
}
else {
@server->Disconnect(@self);
};
}
method : public : Run(param : Base) ~ Nil {
client_name := GetName();
@server->Broadcast("+++ {$client_name} has arrived +++", @self);
message := @client_sock->ReadString();
while(message->Size() > 0 & message->Equals("/quit") = false) {
@server->Broadcast("{$client_name}> {$message}", @self);
message := @client_sock->ReadString();
};
@server->Disconnect(@self);
}
}
} </lang>
Perl
<lang perl>use 5.010; use strict; use warnings;
use threads; use threads::shared;
use IO::Socket::INET; use Time::HiRes qw(sleep ualarm);
my $HOST = "localhost"; my $PORT = 4004;
my @open; my %users : shared;
sub broadcast {
my ($id, $message) = @_;
print "$message\n";
foreach my $i (keys %users) {
if ($i != $id) {
$open[$i]->send("$message\n");
}
}
}
sub sign_in {
my ($conn) = @_;
state $id = 0;
threads->new(
sub {
while (1) {
$conn->send("Please enter your name: ");
$conn->recv(my $name, 1024, 0);
if (defined $name) {
$name = unpack('A*', $name);
if (exists $users{$name}) {
$conn->send("Name entered is already in use.\n");
}
elsif ($name ne ) {
$users{$id} = $name;
broadcast($id, "+++ $name arrived +++");
last;
}
}
}
}
);
++$id; push @open, $conn;
}
my $server = IO::Socket::INET->new(
Timeout => 0,
LocalPort => $PORT,
Proto => "tcp",
LocalAddr => $HOST,
Blocking => 0,
Listen => 1,
Reuse => 1,
);
local $| = 1; print "Listening on $HOST:$PORT\n";
while (1) {
my ($conn) = $server->accept;
if (defined($conn)) {
sign_in($conn);
}
foreach my $i (keys %users) {
my $conn = $open[$i];
my $message;
eval {
local $SIG{ALRM} = sub { die "alarm\n" };
ualarm(500);
$conn->recv($message, 1024, 0);
ualarm(0);
};
if ($@ eq "alarm\n") {
next;
}
if (defined($message)) {
if ($message ne ) {
$message = unpack('A*', $message);
broadcast($i, "$users{$i}> $message");
}
else {
broadcast($i, "--- $users{$i} leaves ---");
delete $users{$i};
undef $open[$i];
}
}
}
sleep(0.1);
}</lang>
Perl 6
(or at least started out that way)
<lang perl6>#!/usr/bin/env perl6
react {
my %connections;
whenever IO::Socket::Async.listen('localhost', 4004) -> $conn {
my $name;
$conn.print: "Please enter your name: ";
whenever $conn.Supply.lines -> $message {
if !$name {
if %connections{$message} {
$conn.print: "Name already taken, choose another one: ";
}
else {
$name = $message;
%connections{$name} = $conn;
broadcast "+++ %s arrived +++", $name;
}
}
else {
broadcast "%s> %s", $name, $message;
}
LAST {
broadcast "--- %s left ---", $name;
%connections{$name}:delete;
$conn.close ;
}
QUIT {
default {
say "oh no, $_";
}
}
}
}
sub broadcast ($format, $from, *@message) {
my $text = sprintf $format, $from, |@message;
say $text;
for %connections.kv -> $name, $conn {
$conn.print: "$text\n" if $name ne $from;
}
}
}</lang>
Notes:
- It operates asynchronously (using IO::Socket::Async), so a slow connection to one client won't affect other clients.
- It accepts messages encoded in UTF-8.
- It tokenizes the message streams at newline boundaries (using the Supply.lines method), which I think makes the most sense for a chat application.
PicoLisp
<lang PicoLisp>#!/usr/bin/picolisp /usr/lib/picolisp/lib.l
(de chat Lst
(out *Sock
(mapc prin Lst)
(prinl) ) )
(setq *Port (port 4004))
(loop
(setq *Sock (listen *Port)) (NIL (fork) (close *Port)) (close *Sock) )
(out *Sock
(prin "Please enter your name: ") (flush) )
(in *Sock (setq *Name (line T)))
(tell 'chat "+++ " *Name " arrived +++")
(task *Sock
(in @
(ifn (eof)
(tell 'chat *Name "> " (line T))
(tell 'chat "--- " *Name " left ---")
(bye) ) ) )
(wait)</lang> After starting the above script, connect to the chat server from two terminals:
Terminal 1 | Terminal 2
---------------------------------+---------------------------------
$ telnet localhost 4004 |
Trying ::1... |
Trying 127.0.0.1... |
Connected to localhost. |
Escape character is '^]'. |
Please enter your name: Ben |
| $ telnet localhost 4004
| Trying ::1...
| Trying 127.0.0.1...
| Connected to localhost.
| Escape character is '^]'.
| Please enter your name: Tom
+++ Tom arrived +++ |
Hi Tom |
| Ben> Hi Tom
| Hi Ben
Tom> Hi Ben |
| How are you?
Tom> How are you? |
Thanks, fine! |
| Ben> Thanks, fine!
| See you!
Tom> See you! |
| ^]
| telnet> quit
--- Tom left --- |
| Connection closed.
| $
Python
<lang python>#!/usr/bin/env python
import socket import thread import time
HOST = "" PORT = 4004
def accept(conn):
"""
Call the inner func in a thread so as not to block. Wait for a
name to be entered from the given connection. Once a name is
entered, set the connection to non-blocking and add the user to
the users dict.
"""
def threaded():
while True:
conn.send("Please enter your name: ")
try:
name = conn.recv(1024).strip()
except socket.error:
continue
if name in users:
conn.send("Name entered is already in use.\n")
elif name:
conn.setblocking(False)
users[name] = conn
broadcast(name, "+++ %s arrived +++" % name)
break
thread.start_new_thread(threaded, ())
def broadcast(name, message):
"""
Send a message to all users from the given name.
"""
print message
for to_name, conn in users.items():
if to_name != name:
try:
conn.send(message + "\n")
except socket.error:
pass
- Set up the server socket.
server = socket.socket(socket.AF_INET, socket.SOCK_STREAM) server.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1) server.setblocking(False) server.bind((HOST, PORT)) server.listen(1) print "Listening on %s" % ("%s:%s" % server.getsockname())
- Main event loop.
users = {} while True:
try:
# Accept new connections.
while True:
try:
conn, addr = server.accept()
except socket.error:
break
accept(conn)
# Read from connections.
for name, conn in users.items():
try:
message = conn.recv(1024)
except socket.error:
continue
if not message:
# Empty string is given on disconnect.
del users[name]
broadcast(name, "--- %s leaves ---" % name)
else:
broadcast(name, "%s> %s" % (name, message.strip()))
time.sleep(.1)
except (SystemExit, KeyboardInterrupt):
break</lang>
Racket
This is a very basic chat server, but it does everything that is needed for this task.
<lang racket>
- lang racket
(define outs (list (current-output-port))) (define ((tell-all who o) line)
(for ([c outs] #:unless (eq? o c)) (displayln (~a who ": " line) c)))
(define ((client i o))
(define nick (begin (display "Nick: " o) (read-line i)))
(define tell (tell-all nick o))
(let loop ([line "(joined)"])
(if (eof-object? line)
(begin (tell "(left)") (set! outs (remq o outs)) (close-output-port o))
(begin (tell line) (loop (read-line i))))))
(define (chat-server listener)
(define-values [i o] (tcp-accept listener)) (for ([p (list i o)]) (file-stream-buffer-mode p 'none)) (thread (client i o)) (set! outs (cons o outs)) (chat-server listener))
(void (thread (λ() (chat-server (tcp-listen 12321))))) ((client (current-input-port) (current-output-port))) </lang>
Ruby
<lang Ruby>require 'gserver'
class ChatServer < GServer
def initialize *args super
#Keep a list for broadcasting messages @chatters = []
#We'll need this for thread safety @mutex = Mutex.new end
#Send message out to everyone but sender def broadcast message, sender = nil #Need to use \r\n for our Windows friends message = message.strip << "\r\n"
#Mutex for safety - GServer uses threads
@mutex.synchronize do
@chatters.each do |chatter|
begin
chatter.print message unless chatter == sender
rescue
@chatters.delete chatter
end
end
end
end
#Handle each connection def serve io io.print 'Name: ' name = io.gets
#They might disconnect return if name.nil?
name.strip!
broadcast "--+ #{name} has joined +--"
#Add to our list of connections
@mutex.synchronize do
@chatters << io
end
#Get and broadcast input until connection returns nil
loop do
message = io.gets
if message
broadcast "#{name}> #{message}", io
else
break
end
end
broadcast "--+ #{name} has left +--"
end
end
- Start up the server on port 7000
- Accept connections for any IP address
- Allow up to 100 connections
- Send information to stderr
- Turn on informational messages
ChatServer.new(7000, '0.0.0.0', 100, $stderr, true).start.join </lang>
Tcl
<lang tcl>package require Tcl 8.6
- Write a message to everyone except the sender of the message
proc writeEveryoneElse {sender message} {
dict for {who ch} $::cmap {
if {$who ne $sender} { puts $ch $message }
}
}
- How to read a line (up to 256 chars long) in a coroutine
proc cgets {ch var} {
upvar 1 $var v
while {[gets $ch v] < 0} {
if {[eof $ch] || [chan pending input $ch] > 256} { return false } yield
} return true
}
- The chatting, as seen by one user
proc chat {ch addr port} {
### CONNECTION CODE ###
#Log "connection from ${addr}:${port} on channel $ch"
fconfigure $ch -buffering none -blocking 0 -encoding utf-8
fileevent $ch readable [info coroutine]
global cmap
try {
### GET THE NICKNAME OF THE USER ### puts -nonewline $ch "Please enter your name: " if {![cgets $ch name]} { return } #Log "Mapping ${addr}:${port} to ${name} on channel $ch" dict set cmap $name $ch writeEveryoneElse $name "+++ $name arrived +++"
### MAIN CHAT LOOP ### while {[cgets $ch line]} { writeEveryoneElse $name "$name> $line" }
} finally {
### DISCONNECTION CODE ### if {[info exists name]} { writeEveryoneElse $name "--- $name left ---" dict unset cmap $name } close $ch #Log "disconnection from ${addr}:${port} on channel $ch"
}
}
- Service the socket by making corouines running [chat]
socket -server {coroutine c[incr count] chat} 4004 set ::cmap {}; # Dictionary mapping nicks to channels vwait forever; # Run event loop</lang>
zkl
On my Linux box, telnet seems to only want to connect to port 23. <lang zkl>const PORT=23;
var users=Dictionary(); // ( handle:socket, ...) pipe:=Thread.Pipe(); // how server tells thread to connect to user
fcn accept(pipe){ // a thread waiting for the server to send a socket
while(socket:=pipe.read()){
println("Somebody is connecting ...");
socket.read(); // telnet stuff
while(True){ // get credentials
reg name; socket.write("Your handle: "); // bottle neck try{ name = socket.read().text.strip() } catch(IOError){ continue } if(users.holds(name)) socket.write("Handle is already in use.\n"); else if(name){ users[name] = socket; chat.launch(name,socket); // thread broadcast(name, "+++ %s arrived +++".fmt(name)); break; // wait for next connection }
}//while }//while
}.launch(pipe); // thread
fcn chat(name,socket){ // a thread, one per user
try{
socket.write("^D to disconnect\n");
while(True){
message:=socket.read().text.strip(); if(message=="\xff\xec") break; // ^D to disconnect. broadcast(name, "%s> %s".fmt(name,message));
}
}catch{} // eg socket pukes
users.del(name); socket.close();
broadcast(name, "--- %s leaves ---".fmt(name));
}
// Send a message to all users from the given name.
fcn broadcast(name, message){ // called from user thread
println(message); // log message to server console
users.pump(Void,'wrap([(toName,socket)]){
if(toName != name) try{ socket.write(message + "\n") } catch(IOError){}
});
}
// Set up the server socket.
server:=Network.TCPServerSocket.open(PORT); println("Listening on %s:%s".fmt(server.hostname,server.port)); server.listen(pipe); // Main event loop </lang>
- Output:
Start the server:
$ sudo ../../../Bin/zkl chatServer.zkl Listening on Octavius:23 Somebody is connecting ... +++ sam arrived +++ --- sam leaves --- Somebody is connecting ... +++ sam arrived +++ Somebody is connecting ... +++ craig arrived +++ craig> this is a test sam> sam i am --- sam leaves --- ^\
Another terminal:
$ telnet localhost Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Your handle: sam ^D to disconnect +++ craig arrived +++ craig> this is a test sam i am ^D Connection closed by foreign host.
And yet another terminal:
$ telnet localhost ... Your handle: craig ^D to disconnect this is a test sam> sam i am --- sam leaves --- Connection closed by foreign host.
- Programming Tasks
- Networking and Web Interaction
- Ada
- AdaSockets
- C
- CoffeeScript
- D
- Erlang
- Go
- Haskell
- Unicon
- Java
- JavaScript
- Julia
- Nim
- Objeck
- Perl
- Perl 6
- Perl 6 examples needing attention
- Examples needing attention
- PicoLisp
- Python
- Racket
- Ruby
- Tcl
- Zkl
- AutoHotkey/Omit
- Lilypond/Omit
- ML/I/Omit
- Mathematica/Omit
- Maxima/Omit
- PARI/GP/Omit
- Retro/Omit
- Stata/Omit