Question

I’m using the POCO c++ libraries, and I’m at a loss. Is there any way to set the source port when sending a UDP datagram? It looks like it’s always set to the destination port, but surely this is possible.

My code looks something like this:

Poco::Net::SocketAddress bcast("255.255.255.255", m_txPort);
DatagramSocket dgs  = DatagramSocket(bcast,false);
dgs.setBroadcast(true);
dgs.sendTo(data,dataLength, broad);

Failing that, I might be switching to Boost – I assume boost can do this, right?

Answer 1

Should work just fine; you pass a SocketAddress with the source address and port into your DatagramSocket constructor which says which local address to bind to; following your example;

Poco::Net::SocketAddress sourceAddress("255.255.255.255", source_port);
DatagramSocket dgs(source_address,false);

Then you pass a separate socketaddress with the destination address and port into SendTo.

Poco::Net::SocketAddress destAddress(destination_address, destination_port);
dgs.setBroadcast(true);
dgs.sendTo(data,dataLength, destAddress);