Setting UDP output port?

m0khz

New to Qt and enjoying the experience, however....

I'm having problems with UDP datagrams??? How do I bind to a known outgoing port?

First I setup a 'discovery receive socket' on port 30303.....

@
//setup Discovery UDP socket on port 30303
discovery_udpSocket = new QUdpSocket(this);
discovery_udpSocket->bind(QHostAddress::Broadcast,30303);
connect(discovery_udpSocket, SIGNAL(readyRead()),this, SLOT(processPendingDatagrams()));
@

Within the event handler for sending datagram I bind socket again

@
// Bind udp socket to Artemis discovery port 30303
discovery_udpSocket = new QUdpSocket(this);
//discovery_udpSocket->bind(QHostAddress::Broadcast,30303); // I tried this as well
discovery_udpSocket->bind(30303);

// Create test data packet
// QByteArray datagram = "Message number : " + QByteArray::number(messageNo);
discovery_udpSocket->writeDatagram(datagram.data(), datagram.size(), QHostAddress::Broadcast,30303);

@

When I run the application and run WireShark to analyse the datagrams, the outgoing port is being randomly set each time I send a datagram?

Any help appreciated :)

Kevin

[EDIT: code formatting, Volker]

dangelog

Would you mind formatting your code using the proper tags?

m0khz

EDIT:
deleted content as it was duplicate of the OP
please use the edit function to reformat the code (I've done that for you, this time)
Volker

m0khz

The reason for needing to know the source & destination ports is due to the fact
I'm using the MicroChip TCP/IP stack were the UDPOpen API Syntax is:

UDP_SOCKET UDPOpen(UDP_PORT localport, NODE_INFO *remoteNode, TCP_PORT remotePort)

where:

localPort [in] = Local UDP port number on which data transfer will occure

remoteNode [in] = Remote host that contains remotePort

RemoteNode [in] = UDP port number on remote host to transfer the data from.

goetz

Have a look at "this forum thread":http://developer.qt.nokia.com/forums/viewthread/4145, they discussed the same topic over there.

m0khz

Thanks for the pointer, from this thread it looks like the send port from within Qt is always random, so it looks like I'll have to write a unique handler for the PIC code...

Kevin

dangelog

Did you read the thread? Just bind the socket before sending. That's it.

m0khz

Yes I have read the thread, I am binding the port before sending (see above), the outgoing port is random.
It looks like I can call a Berkley API from the PIC, eliminating the need for the Qt send port parameter, I'll experiment tonight.

Kevin

dangelog

bind binds a name to a socket. You're simply binding the wrong name, QHostAddress::Broadcast not being an address of any local interface (are you checking the return value of bind? It's probably failing with EADDRNOTAVAIL). Get a copy of TCP/IP Illustrated and/or Unix Network Programming for the gory details.

m0khz

OK that explains it! Thank you, I'll grab a copy of TCP/IP Illustrated, as you suggest, for the 'gory' details :)