/* Connect to the loopback address port 65535, and then test reconnecting to the loopback address port 65534 and print the local 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_in local; socklen_t locallen = sizeof(local); if ( getsockname(fd, (struct sockaddr*) &local, &locallen) < 0 ) err(1, "first getsockname"); 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); struct sockaddr_in cos; memset(&sin, 0, sizeof(cos)); cos.sin_family = AF_INET; cos.sin_addr.s_addr = htobe32(INADDR_LOOPBACK); cos.sin_port = htobe16(65534); if ( connect(fd, (const struct sockaddr*) &cos, sizeof(cos)) < 0 ) err(1, "second connect"); if ( getsockname(fd, (struct sockaddr*) &local, &locallen) < 0 ) err(1, "second getsockname"); char second_port[5 + 1]; getnameinfo((const struct sockaddr*) &local, locallen, host, sizeof(host), second_port, sizeof(second_port), NI_NUMERICHOST | NI_NUMERICSERV); if ( !strncmp(host, "192.168.", strlen("192.168.")) ) printf("192.168.1.x"); else if ( !strncmp(host, "100.82.", strlen("100.82.")) ) printf("192.168.1.x"); else printf("%s", host); printf(":"); if ( !strcmp(port, second_port) ) printf("same port"); else printf("%s", second_port); printf("\n"); return 0; }