93 lines
3.2 KiB
C
93 lines
3.2 KiB
C
#include <sys/types.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <sys/socket.h>
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#include <netdb.h>
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#define BUF_SIZE 500
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int main(int argc, char *argv[])
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{
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struct addrinfo hints;
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struct addrinfo *result, *rp;
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int sfd, s;
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struct sockaddr_storage peer_addr;
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socklen_t peer_addr_len;
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ssize_t nread;
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char buf[BUF_SIZE];
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if (argc != 2) {
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fprintf(stderr, "Usage: %s port\n", argv[0]);
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exit(EXIT_FAILURE);
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}
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memset(&hints, 0, sizeof(struct addrinfo));
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hints.ai_family = AF_UNSPEC; /* Allow IPv4 or IPv6 */
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hints.ai_socktype = SOCK_DGRAM; /* Datagram socket */
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hints.ai_flags = AI_PASSIVE; /* For wildcard IP address */
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hints.ai_protocol = 0; /* Any protocol */
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hints.ai_canonname = NULL;
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hints.ai_addr = NULL;
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hints.ai_next = NULL;
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s = getaddrinfo(NULL, argv[1], &hints, &result);
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if (s != 0) {
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fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s));
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exit(EXIT_FAILURE);
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}
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/* getaddrinfo() returns a list of address structures.
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Try each address until we successfully bind(2).
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If socket(2) (or bind(2)) fails, we (close the socket
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and) try the next address. */
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for (rp = result; rp != NULL; rp = rp->ai_next) {
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sfd = socket(rp->ai_family, rp->ai_socktype,
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rp->ai_protocol);
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if (sfd == -1)
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continue;
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if (bind(sfd, rp->ai_addr, rp->ai_addrlen) == 0)
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break; /* Success */
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close(sfd);
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}
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if (rp == NULL) { /* No address succeeded */
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fprintf(stderr, "Could not bind\n");
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exit(EXIT_FAILURE);
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}
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freeaddrinfo(result); /* No longer needed */
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/* Read datagrams and echo them back to sender */
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for (;;) {
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peer_addr_len = sizeof(struct sockaddr_storage);
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nread = recvfrom(sfd, buf, BUF_SIZE, 0,
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(struct sockaddr *) &peer_addr, &peer_addr_len);
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if (nread == -1)
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continue; /* Ignore failed request */
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char host[NI_MAXHOST], service[NI_MAXSERV];
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s = getnameinfo((struct sockaddr *) &peer_addr,
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peer_addr_len, host, NI_MAXHOST,
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service, NI_MAXSERV, NI_NUMERICSERV);
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if (s == 0) {
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printf("Received %zd bytes from %s:%s\n",
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nread, host, service);
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printf("Data: %s\n", buf);
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} else {
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fprintf(stderr, "getnameinfo: %s\n", gai_strerror(s));
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}
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if (sendto(sfd, buf, nread, 0,
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(struct sockaddr *) &peer_addr,
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peer_addr_len) != nread)
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fprintf(stderr, "Error sending response\n");
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}
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}
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