// The following sample code is just one way to the the multiclient connection, 
// I am sure there is better ways ...
// do not forget to handle the exceptions

static void oneClientConnection(void *aSocket) 
{
  // do the communication using aSocket ...
}

// in your main function 

pthread_t tids[MAX_CONNECTIONS];

// all the necessary work to create, bind and listen ...

client_socket = accept(listen_socket, , );

// you should keep track of the number of connections

if (pthread_create(&(tids[i]), NULL, &oneClientConnection, (void *)&client_socket) !=0 ) {
  perror("pthread_create");
  exit(-2);
}