Distributed programming
You are encouraged to solve this task according to the task description, using any language you may know.
Given two computers on a network, send messages between them. The protocol used may be language-specific or not, and should be suitable for general distributed programming.
E
Protocol: Pluribus
This service cannot be used except by clients which know the URL designating it, messages are encrypted, and the client authenticates the server. However, it is vulnerable to denial-of-service by any client knowing the URL.
Server
(The protocol is symmetric; this program is the server only in that it is the one which is started first and exports an object.)
def storage := [].diverge() def logService { to log(line :String) { storage.push([timer.now(), line]) } to search(substring :String) { var matches := [] for [time, line] ? (line.startOf(substring) != -1) in storage { matches with= [time, line] } return matches } } introducer.onTheAir() def sturdyRef := makeSturdyRef.temp(logService) println(<captp>.sturdyToURI(sturdyRef)) interp.blockAtTop()
This will print the URL of the service and run it until aborted.
Client
The URL provided by the server is given as the argument to this program.
def [uri] := interp.getArgs() introducer.onTheAir() def sturdyRef := <captp>.sturdyFromURI(uri) def logService := sturdyRef.getRcvr() logService <- log("foot") logService <- log("shoe") println("Searching...") when (def result := logService <- search("foo")) -> { for [time, line] in result { println(`At $time: $line`) } }
JoCaml
Minimalistic distributed logger with synchronous channels using the join calculus on top of OCaml.
Server
open Printf let create_logger () = def log(text) & logs(l) = printf "Logged: %s\n%!" text; logs((text, Unix.gettimeofday ())::l) & reply to log or search(text) & logs(l) = logs(l) & reply List.filter (fun (line, _) -> line = text) l to search in spawn logs([]); (log, search) def wait() & finished() = reply to wait let register name service = Join.Ns.register Join.Ns.here name service let () = let log, search = create_logger () in register "log" log; register "search" search; Join.Site.listen (Unix.ADDR_INET (Join.Site.get_local_addr(), 12345)); wait ()
Client
open Printf let ns_there = Join.Ns.there (Unix.ADDR_INET (Join.Site.get_local_addr(), 12345)) let lookup name = Join.Ns.lookup ns_there name let log : string -> unit = lookup "log" let search : string -> (string * float) list = lookup "search" let find txt = printf "Looking for %s...\n" txt; List.iter (fun (line, time) -> printf "Found: '%s' at t = %f\n%!" (String.escaped line) time) (search txt) let () = log "bar"; find "foo"; log "foo"; log "shoe"; find "foo"