multithreading - Java Socket client/server pair can only send one message at a time -

a successful conversation can carried out between client , server. if 1 message sent between client , server.

example (works):

client: hello server: helloo client: time server: let me 

example (does not work):

client: hello server: helloo server: *how today* server: *test message* client: yes 

the messages between asterisks not appear on client side untill client sends 2 messages. understand seems work net-message system number of messages sent server has equal n+-1 number of messages sent client, messages shown.

client side code:

try {             socket client_socket= new socket(hostname,port_number);             printwriter output = new printwriter(client_socket.getoutputstream(),true);             bufferedreader input = new bufferedreader(new inputstreamreader(client_socket.getinputstream()));             bufferedreader stdin=new bufferedreader(new inputstreamreader(system.in));              string fromuser,fromserver;             while ((fromserver=input.readline())!=null) {                 system.out.println("server: "+fromserver);                 if (fromserver.equals("quit")) {                     break;                 }                  fromuser=stdin.readline();                 if (fromuser!=null) {                     system.out.println("client: "+fromuser);                     output.println(fromuser);                 }              }          } 

server side code:

try {             serversocket server_socket=new serversocket(port_number);             socket client_socket= server_socket.accept();             printwriter output = new printwriter(client_socket.getoutputstream(),true);             bufferedreader input = new bufferedreader(new inputstreamreader(client_socket.getinputstream()));             bufferedreader stdin=new bufferedreader(new inputstreamreader(system.in));             output.println("established");             string fromuser, fromserver;             while ((fromuser=input.readline())!=null) {                 system.out.println("client: "+fromuser);                 if (fromuser.equals("quit")) {                     break;                 }                  fromserver=stdin.readline();                 if (fromserver!=null) {                     system.out.println("server: "+fromserver);                     output.println(fromserver);                 }             }          } 

looking @ code can see why happen, because sop after while loop initialization stops code waiting 1 line of input, , waits send own sentence, before receiving another. tried putting these within if statements, results in no communication @ all.

i cant seem figure out how fix this.

if requires threads, there way? (i'm not familiar threads)

depending on nature of program, advise use more threads handle messaging.

lets start server: if server can have multiple clients, wise distinguish every client thread, example:

            serversocket ss;              try {                 ss = new serversocket(portin);                 while (true) {                     socket s = ss.accept();                     // option 1: runnable class                     new thread(new customrunnableclass(s)).start();                 }             } catch (ioexception e) {                 e.printstacktrace();             } 

or if dont want "session manager" custom runnable class, can replace line new thread(new customrunnableclass(s)).start(); following

new thread(new runnable() {    @override    public void run() {         new someclass().runthisclass();    } } 

on client side suggest whatever class listens new messages sockets distinguished new thread:

private void startlistening() {     new thread(new runnable() {         @override         public void run() {             for(;;) {                 string msg = dis.readutf();                 system.out.println("  ----- recieved new message -----\n" + msg);                 (imessagelistener listener : listeners) {                     try {                         listener.onmessagerecieved(msg);                     } catch (exception e) {                      }                 }             }         }     }).start(); } 

this way client listens message received client , runs method handle them upon receiving, , not hung in meanwhile.

hope helpful.