multichat uses BSD TCP sockets and libpthread to handle new connections. In the main loop, it keeps listening for new connections, and when a new client arrives, a new thread is created, which receives messages from this client and repasses this message to all connected clients.
The main loop is simply:
while(1) {
c = new Client();
t = new MyThread();
//Blocks here;
c->sock = accept(serverSock, (struct sockaddr *) &clientAddr, &cliSize);
if(c->sock < 0) {
cerr << "Error on accept";
}
else {
t->Create((void *) Server::HandleClient, c);
}
}
This kind of behavior may be useful, because we can use the blocking nature from accept() and from each client's recv() to keep each thread blocked and leave the scheduling of these threads to the OS. One downside of this approach is that we must be extra careful with shared variables, since several threads may be trying to access them 'simultaneously'. To prevent concurrency problems, a simple mutex is responsible for granting/denying access to shared resources, as in Server::SendToAll() function:
//Acquire the lock - Blocks here until the lock is acquired
MyThread::LockMutex("'SendToAll()'");
for(size_t i=0; i<clients.size(); i++) {
n = send(Server::clients[i].sock, message, strlen(message), 0);
cout << n << " bytes sent." << endl;
}
//Release the lock
MyThread::UnlockMutex("'SendToAll()'");
> $ make
g++ -Wall -g -c src/main.cpp -o obj/main.o
g++ -Wall -g -c src/mythread.cpp -o obj/mythread.o
g++ -Wall -g -c src/server.cpp -o obj/server.o
g++ -Wall -g -c src/client.cpp -o obj/client.o
g++ -Wall -g -lpthread -o ./bin/chat ./obj/main.o ./obj/mythread.o ./obj/server.o ./obj/client.o
> $ /bin/chat
Running!
Mutex initialized.
- telnet:
> $ telnet 127.0.0.1 30777
Trying 127.0.0.1...
Connected to 127.0.0.1.
Escape character is '^]'.
Hello from telnet!
<Client n.0>: Hello from telnet!
<Client n.1>: Hello from netcat!
On Android i recommend "TCP Telnet Terminal V1.13" from Author mightyIT.
- netcat:
> $ netcat 127.0.0.1 30777
<Client n.0>: Hello from telnet!
Hello from netcat!
<Client n.1>: Hello from netcat!
-Check threads with
watch ps -C chat -L
-if connecting from Putty: "Local line editing" in "Terminal" panel has to be enabled.
This software is released with no warranties and is under public domain.
React
Typescript
Django
Laravel
Facebook
Microsoft
Google
Alibaba
D3
Tencent