Qt 4.8 QTcpServer strange behaviour.

flomop

Hi,
I have a following code:

QTcpSocket client;
QTcpServer server;

qDebug() << server.listen( QHostAddress::Any  //true
                         , 36235);
usleep( 1000000);

client.connectToHost( QHostAddress::LocalHost
                                       , 36235);

qDebug() << client.error(); //QAbstractSocket::UnknownSocketError

usleep( 1000000);
QTcpSocket *t = server.nextPendingConnection();

client.waitForConnected(-1); //wait forever!

qDebug() << "client.state()" << client.state();
qDebug() << client.write( QByteArray( "12345"));
qDebug() << "t.state(): " << t->state();

qDebug() << t->bytesAvailable();
qDebug() << t->read( 5);

So, it gives me:

true
QAbstractSocket::UnknownSocketError
client.state() QAbstractSocket::ConnectedState
5

And after that I got segfault because t is 0x00.

I don't want to use Qt Signals/Slots system, so all the connect magic is not for me.

➜ ss -at

State       Recv-Q Send-Q          Local Address:Port                           Peer Address:Port                
LISTEN      0      0                           *:36235                                     *:*                    
LISTEN      0      0                           *:ssh                                       *:*                    
ESTAB       0      0               192.168.10.96:33360                        151.101.129.69:http                 
ESTAB       0      0               192.168.10.96:45112                        74.125.232.230:https                
CLOSE-WAIT  38     0               192.168.10.96:60620                        107.20.174.100:https                
CLOSE-WAIT  147    0               192.168.10.96:35470                            192.0.73.2:https                

telnet gave me:

➜  telnet localhost 36235

Trying ::1...
Connection failed: Connection refused
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.

What i'm doing wrong?
What this UnknownSocketError means?
What should I do?

SGaist

Hi and welcome to devnet,

Then you should use waitForConnected to ensure the connection was established.

Out of curiosity, why not use Qt's signals and slots mechanism ?

flomop

@SGaist Hi. Thanks for answer!

Using of waitForNewConnection makes no difference.

I have quite a complicated code which I don't want to complicate more with async logic.

SGaist

Can you explain what you are trying to achieve ? Currently it looks like you are trying to setup a server in your application and connect to the said server from the same application.