xu: unix socket echo client

xu.erl

-module(xu).

-export([start/1,start/4]).
-export([connect/5]).

-define(RESPONSE_TIMEOUT, 20000).

-define(NUM_CLIENTS, 10).
-define(DELAY, 1000).
-define(NUM_REQUESTS, 100).

start(File) ->
    start(File, ?NUM_CLIENTS, ?DELAY, ?NUM_REQUESTS).
start(File, NumClients, Delay, NumRequests) ->
    Packet = binary:copy(<<"x">>, 100),
    [ spawn_link(?MODULE, connect, [File, Client, Packet, Delay, NumRequests]) || Client <- lists:seq(1, NumClients) ].

connect(File, Client, Packet, Delay, N) ->
    timer:sleep(crypto:rand_uniform(1, 5 * 1000)), % stagger the requests (milliseconds)
    error_logger:info_report([{connecting, Client, N}]),
    {ok, Ref} = gen_unix:start(),
    {ok, Socket} = gen_unix:connect(Ref, File),
    request(Client, Ref, Socket, Packet, Delay, N).

request(Client,_,_,_,_,0) ->
    error_logger:info_report([{complete, {client,Client}}]),
    run_complete;
request(Client, Ref, Socket, Packet, Delay, N) ->
    Size = byte_size(Packet),
    ok = gen_unix:sendmsg(Ref, Socket, <<Size:4/unsigned-integer-unit:8, Packet/binary>>, []),
    {ok, <<Size:4/unsigned-integer-unit:8, Packet/binary>>, _, _} = gen_unix:recvmsg(Ref, Socket, Size+4, 0),
    request(Client, Ref, Socket, Packet, Delay, N-1).