#include #include #include #include #include #include #include #define BUF_SIZE 500 int main(int argc, char *argv[]) { struct addrinfo hints; struct addrinfo *result, *rp; int sfd, s, j; size_t len; ssize_t nread; char buf[BUF_SIZE]; if (argc < 3) { fprintf(stderr, "Usage: %s host port msg...\n", argv[0]); exit(EXIT_FAILURE); } /* Obtain address(es) matching host/port */ memset(&hints, 0, sizeof(struct addrinfo)); hints.ai_family = AF_UNSPEC; /* Allow IPv4 or IPv6 */ hints.ai_socktype = SOCK_DGRAM; /* Datagram socket */ hints.ai_flags = 0; hints.ai_protocol = 0; /* Any protocol */ s = getaddrinfo(argv[1], argv[2], &hints, &result); if (s != 0) { fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s)); exit(EXIT_FAILURE); } /* getaddrinfo() returns a list of address structures. Try each address until we successfully connect(2). If socket(2) (or connect(2)) fails, we (close the socket and) try the next address. */ for (rp = result; rp != NULL; rp = rp->ai_next) { sfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol); if (sfd == -1) continue; if (connect(sfd, rp->ai_addr, rp->ai_addrlen) != -1) break; /* Success */ close(sfd); } if (rp == NULL) { /* No address succeeded */ fprintf(stderr, "Could not connect\n"); exit(EXIT_FAILURE); } freeaddrinfo(result); /* No longer needed */ /* Send remaining command-line arguments as separate datagrams, and read responses from server */ for (j = 3; j < argc; j++) { len = strlen(argv[j]) + 1; /* +1 for terminating null byte */ if (len + 1 > BUF_SIZE) { fprintf(stderr, "Ignoring long message in argument %d\n", j); continue; } if (write(sfd, argv[j], len) != len) { fprintf(stderr, "partial/failed write\n"); exit(EXIT_FAILURE); } nread = read(sfd, buf, BUF_SIZE); if (nread == -1) { perror("read"); exit(EXIT_FAILURE); } printf("Received %ld bytes: %s\n", (long) nread, buf); } exit(EXIT_SUCCESS); }