udp recvfrom() returns no IP address

[JediDan]

Hello,

I have a socket app performing recvfrom(...) on a UDP socket. The data comes across fine, but I don't get an IP address in the sockaddr struct, although I do get a port... Code:

sockaddr_in sourceAddr;
socklen_t addrLen;

recvfrom(socketfd, buffer, avail, 0, (sockaddr*)&sourceAddr, &addrLen);

inet_ntoa(sourceAddr.sin_addr) gives "0.0.0.0"

ntohs(sourceAddr.sin_port) gives "50717" (or whatever the remote port was, varies of course).

This is running on a Linux box with g++ 4.1.1, and the problem happens with UDP packets sent from either another Linux machine or Windows.

I also notice that when I bind this UDP port, it thinks it's IP address is also 0.0.0.0, although when I bind TCP sockets elsewhere in the app, they correctly determine the machine's IP.

Any ideas?

Thanks,

Dan

 

[fpmurphy]

Have you done

socklen_t addrLen=sizeof(sourceAddr);

before the recvfrom() statement?