Multithreading for callback function in C++ - c++

Question

Im implementing a chat application using Jabber/XMPP and gloox framework which should send and receive messages concurrently in Ubuntu Linux.
My current code implementation is :
int main()
{
...
int temp = pthread_create(&iSend, NULL, SendMessage, &b);
int temp1 = pthread_create(&iRecv, NULL, ConnServer, &b);
}
void* ConnServer(void *athis)
{
UserClient *t = (UserClient*)athis;
t->ConnecttosServer();
}
bool UserClient::ConnecttosServer()
{
//JID jid( "map#jo-hely.hu/gloox" );
j = new Client( iUserJid, iUser.getPassword() );
j->registerMessageHandler( this);
j->registerConnectionListener( this );
j->registerMessageSessionHandler(this);
bool result = j->connect(false);
if(result == true)
{
iConnected = true;
ConnectionError er = ConnNoError;
ConnectionError er1 = ConnNoError;
while(er == ConnNoError || er1 == ConnNoError)
{
er = j->recv(500000);
sleep(2);
}
delete j;
}
...
}
void* SendMessage(void * athis )// JID *aDest)
{
UserClient *t = (UserClient*)athis;
//JID *t = (JID)dest;
string ip ;
cout << "enter here";
cin >> ip;
if(t->iConnected == true)
{
if(t->iMessageSession == NULL )
{
string aBody = "hello";
MessageSession *session = new MessageSession(t->j, t->iDestJid);
session->registerMessageHandler(t);
session->send(aBody.c_str());
}
}
}
The problem faced is both the threads are created and pthread_join( ) is called for both.
The iSend thread is scheduled first but gets suspended at cin. Once the recv( ) function is called, which runs in iRecv thread, the recv call back function handleMessage( ) is called. However the control never shifts back to the iSend thread which should call SendMessage( ) function.
Please help

Answer 1

I cannot see in there how SendMessage ever sends more than one "hello" message.
There are various memory issues here of course, eg j won't get deleted at all if connect failed, and as its scope is function-only there is no real need to create it with new at all.

Answer 2

You cannot count on the iSend thread being scheduled first. That is completely up to the operating system.