I'm using socket_server from this tutorial and the following code for a client and server:
Server:
-module(echo_server).
-export([start/0, loop/1]).
% echo_server specific code
start() ->
spawn(socket_server, start, [?MODULE, 7000, {?MODULE, loop}]).
loop(Socket) ->
case gen_tcp:recv(Socket, 0) of
{ok, Message} ->
Msg = binary_to_term(Message),
case Msg of
start ->
io:format("Got start message on socket ~p.~n", [Socket]),
send_count(Socket, 10),
gen_tcp:close(Socket);
Other ->
io:format("Got message on socket ~p: ~p~n",
[Socket, Other])
end;
{error, closed} ->
io:format("Got closed message on socket ~p.~n", [Socket]),
ok;
Error ->
io:format("Got bad message: ~p on socket ~p.~n", [Error, Socket])
end.
send_count(_Socket, 0) ->
ok;
send_count(Socket, Num) ->
io:format("Sending ~p to ~p.~n", [Num, Socket]),
gen_tcp:send(Socket, term_to_binary(Num)),
send_count(Socket, Num - 1).
Client:
-module(echo_client).
-export([start/0, do_stuff/0]).
send(Socket, Msg) ->
gen_tcp:send(Socket, term_to_binary(Msg)).
start() ->
dbg:tracer(),
Pid = spawn(?MODULE, do_stuff, []),
dbg:p(Pid, r).
do_stuff() ->
case gen_tcp:connect("localhost", 7000, [binary, {packet, 0}]) of
{ok, Socket} ->
send(Socket, start),
rx_loop(Socket);
Error ->
io:format("Error connecting to server: ~p~n", [Error])
end.
rx_loop(Socket) ->
receive
{tcp, Socket, Message} ->
Msg = binary_to_term(Message),
io:format("Received message: ~p~n", [Msg]),
rx_loop(Socket)
after 5000 ->
finish_loop(Socket)
end.
finish_loop(Socket) ->
receive
{tcp, Socket, Message} ->
Msg = binary_to_term(Message),
io:format("Received message: ~p~n", [Msg]),
rx_loop(Socket);
{tcp_closed, Socket} ->
io:format("Server terminated connection.~n"),
exit(normal);
Error ->
io:format("Received bad message: ~p~n", [Error]),
rx_loop(Socket)
end.
I'm invoking echo_server:start() and echo_client:start() from different shells on the same system, in that order. Here's what I see:
The server seems to work just fine.
1>echo_server:start().
<0.39.0>
Got start message on socket #Port<0.2041>.
Sending 10 to #Port<0.2041>.
Sending 9 to #Port<0.2041>.
Sending 8 to #Port<0.2041>.
Sending 7 to #Port<0.2041>.
Sending 6 to #Port<0.2041>.
Sending 5 to #Port<0.2041>.
Sending 4 to #Port<0.2041>.
Sending 3 to #Port<0.2041>.
Sending 2 to #Port<0.2041>.
Sending 1 to #Port<0.2041>.
The client doesn't quite get all the messages right:
2> echo_client:start().
{ok,[{matched,nonode@nohost,1}]}
3> (<0.41.0>) << {code_server,{module,gen_tcp}}
(<0.41.0>) << {code_server,{module,inet_tcp}}
(<0.41.0>) << {#Ref<0.0.0.74>,{ok,<0.43.0>}}
(<0.41.0>) << {#Ref<0.0.0.76>,
{ok,<<4,0,0,0,2,127,0,0,1,127,0,0,1,0,0,0,3,108,111,99,97,108,
104,111,115,116,0,105,112,54,45,108,111,99,97,108,104,
111,115,116,0,105,112,54,45,108,111,111,112,98,97,99,
107,0>>}}
(<0.41.0>) << {inet_async,#Port<0.2058>,0,ok}
(<0.41.0>) << {inet_reply,#Port<0.2058>,ok}
Received message: 10
3> (<0.41.0>) << {tcp,#Port<0.2058>,<<131,97,10>>}
Received message: 9
3> (<0.41.0>) << {io_reply,<0.25.0>,ok}
(<0.41.0>) << timeout
(<0.41.0>) << {tcp,#Port<0.2058>,<<131,97,9>>}
(<0.41.0>) << {io_reply,<0.25.0>,ok}
Received message: 8
Received message: 5
Received message: 4
Received message: 3
Received message: 2
Received message: 1
3> (<0.41.0>) << timeout
(<0.41.0>) << {tcp,#Port<0.2058>,<<131,97,8,131,97,7,131,97,6>>} %% <---This guy here
(<0.41.0>) << {io_reply,<0.25.0>,ok}
(<0.41.0>) << {tcp,#Port<0.2058>,<<131,97,5>>}
(<0.41.0>) << timeout
(<0.41.0>) << {io_reply,<0.25.0>,ok}
(<0.41.0>) << timeout
(<0.41.0>) << {tcp,#Port<0.2058>,<<131,97,4>>}
(<0.41.0>) << {io_reply,<0.25.0>,ok}
(<0.41.0>) << timeout
(<0.41.0>) << {tcp,#Port<0.2058>,<<131,97,3>>}
(<0.41.0>) << {io_reply,<0.25.0>,ok}
(<0.41.0>) << timeout
(<0.41.0>) << {tcp,#Port<0.2058>,<<131,97,2>>}
(<0.41.0>) << {io_reply,<0.25.0>,ok}
(<0.41.0>) << timeout
(<0.41.0>) << {tcp,#Port<0.2058>,<<131,97,1>>}
(<0.41.0>) << {io_reply,<0.25.0>,ok}
(<0.41.0>) << {tcp_closed,#Port<0.2058>}
(<0.41.0>) << timeout
Server terminated connection.
3> (<0.41.0>) << timeout
(<0.41.0>) << {io_reply,<0.25.0>,ok}
(<0.41.0>) << timeout
If I look at the network traffic on lo, I see nice clean PSH/ACK pairs for each number counting down. The line I pointed at above shows two packets showing up in a single message: 7 and 6. Those came across the network as two separate TCP packets. Anyone have any idea why they're being smushed together or how to un-smush them?
