/* Connect to loopback address port 65535, unconnect, and then test the remote address. */ #include "udp.h" int main(void) { int fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); if ( fd < 0 ) err(1, "socket"); struct sockaddr_in sin; memset(&sin, 0, sizeof(sin)); sin.sin_family = AF_INET; sin.sin_addr.s_addr = htobe32(INADDR_LOOPBACK); sin.sin_port = htobe16(65535); if ( connect(fd, (const struct sockaddr*) &sin, sizeof(sin)) < 0 ) err(1, "first connect"); struct sockaddr cos; memset(&cos, 0, sizeof(cos)); cos.sa_family = AF_UNSPEC; if ( connect(fd, (const struct sockaddr*) &cos, sizeof(cos)) < 0 ) err(1, "second connect"); struct sockaddr_in local; socklen_t locallen = sizeof(local); if ( getpeername(fd, (struct sockaddr*) &local, &locallen) < 0 ) err(1, "getpeername"); char host[INET_ADDRSTRLEN + 1]; char port[5 + 1]; getnameinfo((const struct sockaddr*) &local, locallen, host, sizeof(host), port, sizeof(port), NI_NUMERICHOST | NI_NUMERICSERV); printf("%s:%s\n", host, port); return 0; }