Concurrence in Erlang - concurrency

Question

I'm new in erlang and I'm trying to implement a register/login server. I have a function to register new users, and it works well:
reg(Sock) ->
receive
{tcp, _, Usr} ->
io:format("User: ~p ~n",[Usr])
end,
gen_tcp:send(Sock, [Usr]),
receive
{tcp, _, Pass} ->
io:format(" a pass ~p~n",[Pass])
end,
gen_tcp:send(Sock, [Pass]),
receive
{tcp, _, Msg} ->
case Msg of
<<"condutor\n">> ->
condutor ! {register, {Usr, Pass}};
<<"passageiro\n">> ->
io:format("passageiro~n")
end
end.
But now I want to have another function that controlls if a user wants to login or register, and send the proper function. But when I add this function it doesn't read the input of the user:
gestor(Sock) ->
receive
{tcp, _, Msg} ->
case Msg of
<<"login\n">> ->
login(Sock);
<<"registo\n">> ->
gen_tcp:send(Sock, "OK"),
reg(Sock)
end
end.
It receives the option of the user, sends him to the right function but then it doesn't read anything, I can't understand this because if I call the function reg directly it works fine, but if I call that function from another function, I can't read nothing from the socket.
If anyone could help me I would apreciate it very much.
EDITED:
Thanks a lot for your replies, I'm trying to implement a Java client and a Erlang server communicating through a Tcp socket, it's intended that the user types "registo" than a username, a password, and "condutor" or "passageiro".
The socket works fine because if I call reg(sock) instead of gestor(Sock) everything works as expected, the problem is when I call reg(Sock) inside gestor(Sock) in this case I can't receive the user input in reg function.
-module(server2).
-export([server/1]).
server(Port) ->
{ok, LSock} = gen_tcp:listen(Port, [binary, {packet, line}, {reuseaddr, true}]),
Condutor = spawn(fun()-> regUtente([]) end),
register(condutor, Condutor),
acceptor(LSock).
acceptor(LSock) ->
{ok, Sock} = gen_tcp:accept(LSock),
spawn(fun() -> acceptor(LSock) end),
io:format("Ligação estabelecida~n"),
% reg(Sock). --- Caling reg directly, without passing through gestor WORKS FINE.
gestor(Sock).
Java Client:
import java.io.*;
import java.net.*;
public class EchoClient {
public static void main(String[] args) throws IOException {
if (args.length != 2) {
System.err.println(
"Usage: java EchoClient <host name> <port number>");
System.exit(1);
}
String hostName = args[0];
int portNumber = Integer.parseInt(args[1]);
try (
Socket echoSocket = new Socket(hostName, portNumber);
PrintWriter out =
new PrintWriter(echoSocket.getOutputStream(), true);
BufferedReader in =
new BufferedReader(
new InputStreamReader(echoSocket.getInputStream()));
BufferedReader stdIn =
new BufferedReader(
new InputStreamReader(System.in))
) {
String userInput;
while ((userInput = stdIn.readLine()) != null) {
out.println(userInput);
System.out.println("echo: " + in.readLine());
}
} catch (UnknownHostException e) {
System.err.println("Don't know about host " + hostName);
System.exit(1);
} catch (IOException e) {
System.err.println("Couldn't get I/O for the connection to " +
hostName);
System.exit(1);
}
}
}

Answer 1

Send "OK\n" as a response to "registo." Your java code is using readline so you need a line terminator.