S P wrote: > I am writing a simple program in which a machine A > broadcasts UDP messages on a subnet. Another machine B > on the same subnet receives this message using > "recvfrom". > > int recvfrom(int s, void *buf, size_t len, int flags, > struct sockaddr *from, socklen_t *fromlen); > > The last 2 parameters of recvfrom give information > about the sender of the message - machine A. The > information is IP address, port number, and family > (AF_INET etc.). > If I compile the program using gcc option -O2, > recvfrom works & receives the message correctly, but > no information about the sender. If option -O2 is not > used, this works fine. Did you initialise the fromlen argument? From the recvfrom(2) manpage: The argument fromlen is a value-result parameter, initial ized to the size of the buffer associated with from, and modified on return to indicate the actual size of the address stored there. I.e.: struct sockaddr_in from; socklen_t fromlen = sizeof(from); recvfrom(skt, buf, len, flags, (struct sockaddr *) &from, &fromlen); -- Glynn Clements <glynn.clements@virgin.net> - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
