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POUDP socket port allocation failure
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copied!<p>I am creating a winsock UDP program. code i am using is shown below.</p> <p>I am always getting port assignment error.</p> <p>I am not able to understand why port always allocated is zero. If some can help me with this....</p> <pre><code>void UDPecho(const char *, const char *); void errexit(const char *, ...); #define LINELEN 128 #define WSVERS MAKEWORD(2, 0) void main(int argc, char *argv[]) { char *host = "localhost"; char *service = "echo"; WSADATA wsadata; switch (argc) { case 1: host = "localhost"; break; case 3: service = argv[2]; /* FALL THROUGH */ case 2: host = argv[1]; break; default: fprintf(stderr, "usage: UDPecho [host [port]]\n"); exit(1); } if (WSAStartup(WSVERS, &wsadata)) errexit("WSAStartup failed\n"); UDPecho(host, service); WSACleanup(); exit(0); } void UDPecho(const char *host, const char *service) { char buf[LINELEN+1]; SOCKET s; int nchars; struct hostent *phe; struct servent *pse; struct protoent *ppe; struct sockaddr_in sin, my_sin; int type, status, client_port, size; char *transport = "udp"; memset(&sin, 0, sizeof(sin)); sin.sin_family = AF_INET; /* Map service name to port number */ if ( pse = getservbyname(service, transport) ) sin.sin_port = pse->s_port; else if ( (sin.sin_port = htons((u_short)atoi(service)))== 0) errexit("can't get \"%s\" service entry\n", service); /* Map host name to IP address, allowing for dotted decimal */ if ( phe = gethostbyname(host) ) memcpy(&sin.sin_addr, phe->h_addr, phe->h_length); else if ( (sin.sin_addr.s_addr = inet_addr(host)) == INADDR_NONE) errexit("can't get \"%s\" host entry\n", host); printf("Our target server is at address %s\n", inet_ntoa(sin.sin_addr)); printf("The size of an FD set is %d\n", sizeof(FD_SET)); /* Map protocol name to protocol number */ if ( (ppe = getprotobyname(transport)) == 0) errexit("can't get \"%s\" protocol entry\n", transport); /* Use protocol to choose a socket type */ if (strcmp(transport, "udp") == 0) type = SOCK_DGRAM; else type = SOCK_STREAM; /* Allocate a socket */ s = socket(PF_INET, type, ppe->p_proto); if (s == INVALID_SOCKET) errexit("can't create socket: %d\n", GetLastError()); size = sizeof(sin); memset(&my_sin, 0, sizeof(sin)); getsockname (s, (struct sockaddr *) &my_sin, &size); client_port = ntohs(my_sin.sin_port); if (client_port != 0) printf ("We are using port %2d\n", client_port); else { printf("No port assigned yet\n"); } } void errexit(const char *format, ...) { va_list args; va_start(args, format); vfprintf(stderr, format, args); va_end(args); WSACleanup(); exit(1); } </code></pre>

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