UDP server Code
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2023-11-30 09:08:34
The programs are an echo server and client for UDP datagrams. ......
code example:
the following programs demonstrate the use of getaddrinfo(), gai_strerror(), freeaddrinfo(), and getnameinfo(). the programs are an echo server and client for udp datagrams.
服务器端程序:
1 ###server program 2 3 #include <sys/types.h> 4 #include <stdio.h> 5 #include <stdlib.h> 6 #include <unistd.h> 7 #include <string.h> 8 #include <sys/socket.h> 9 #include <netdb.h> 10 11 #define buf_size 500 12 13 int 14 main(int argc, char *argv[]) 15 { 16 struct addrinfo hints; 17 struct addrinfo *result, *rp; 18 int sfd, s; 19 struct sockaddr_storage peer_addr; 20 socklen_t peer_addr_len; 21 ssize_t nread; 22 char buf[buf_size]; 23 24 if (argc != 2) { 25 fprintf(stderr, "usage: %s port\n", argv[0]); 26 exit(exit_failure); 27 } 28 29 memset(&hints, 0, sizeof(struct addrinfo)); 30 hints.ai_family = af_unspec; /* allow ipv4 or ipv6 */ 31 hints.ai_socktype = sock_dgram; /* datagram socket */ 32 hints.ai_flags = ai_passive; /* for wildcard ip address */ 33 hints.ai_protocol = 0; /* any protocol */ 34 hints.ai_canonname = null; 35 hints.ai_addr = null; 36 hints.ai_next = null; 37 38 s = getaddrinfo(null, argv[1], &hints, &result); 39 if (s != 0) { 40 fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s)); 41 exit(exit_failure); 42 } 43 44 /* getaddrinfo() returns a list of address structures. 45 try each address until we successfully bind(2). 46 if socket(2) (or bind(2)) fails, we (close the socket 47 and) try the next address. */ 48 49 for (rp = result; rp != null; rp = rp->ai_next) { 50 sfd = socket(rp->ai_family, rp->ai_socktype, 51 rp->ai_protocol); 52 if (sfd == -1) 53 continue; 54 55 if (bind(sfd, rp->ai_addr, rp->ai_addrlen) == 0) 56 break; /* success */ 57 58 close(sfd); 59 } 60 61 if (rp == null) { /* no address succeeded */ 62 fprintf(stderr, "could not bind\n"); 63 exit(exit_failure); 64 } 65 66 freeaddrinfo(result); /* no longer needed */ 67 68 /* read datagrams and echo them back to sender */ 69 70 for (;;) { 71 peer_addr_len = sizeof(struct sockaddr_storage); 72 nread = recvfrom(sfd, buf, buf_size, 0, 73 (struct sockaddr *) &peer_addr, &peer_addr_len); 74 if (nread == -1) 75 continue; /* ignore failed request */ 76 77 char host[ni_maxhost], service[ni_maxserv]; 78 79 s = getnameinfo((struct sockaddr *) &peer_addr, 80 peer_addr_len, host, ni_maxhost, 81 service, ni_maxserv, ni_numericserv); 82 if (s == 0) 83 printf("received %zd bytes from %s:%s\n", 84 nread, host, service); 85 else 86 fprintf(stderr, "getnameinfo: %s\n", gai_strerror(s)); 87 88 if (sendto(sfd, buf, nread, 0, 89 (struct sockaddr *) &peer_addr, 90 peer_addr_len) != nread) 91 fprintf(stderr, "error sending response\n"); 92 } 93 }
客户端程序:
1 ###client program 2 3 #include <sys/types.h> 4 #include <sys/socket.h> 5 #include <netdb.h> 6 #include <stdio.h> 7 #include <stdlib.h> 8 #include <unistd.h> 9 #include <string.h> 10 11 #define buf_size 500 12 13 int 14 main(int argc, char *argv[]) 15 { 16 struct addrinfo hints; 17 struct addrinfo *result, *rp; 18 int sfd, s, j; 19 size_t len; 20 ssize_t nread; 21 char buf[buf_size]; 22 23 if (argc < 3) { 24 fprintf(stderr, "usage: %s host port msg...\n", argv[0]); 25 exit(exit_failure); 26 } 27 28 /* obtain address(es) matching host/port */ 29 30 memset(&hints, 0, sizeof(struct addrinfo)); 31 hints.ai_family = af_unspec; /* allow ipv4 or ipv6 */ 32 hints.ai_socktype = sock_dgram; /* datagram socket */ 33 hints.ai_flags = 0; 34 hints.ai_protocol = 0; /* any protocol */ 35 36 s = getaddrinfo(argv[1], argv[2], &hints, &result); 37 if (s != 0) { 38 fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(s)); 39 exit(exit_failure); 40 } 41 42 /* getaddrinfo() returns a list of address structures. 43 try each address until we successfully connect(2). 44 if socket(2) (or connect(2)) fails, we (close the socket 45 and) try the next address. */ 46 47 for (rp = result; rp != null; rp = rp->ai_next) { 48 sfd = socket(rp->ai_family, rp->ai_socktype, 49 rp->ai_protocol); 50 if (sfd == -1) 51 continue; 52 53 if (connect(sfd, rp->ai_addr, rp->ai_addrlen) != -1) 54 break; /* success */ 55 56 close(sfd); 57 } 58 59 if (rp == null) { /* no address succeeded */ 60 fprintf(stderr, "could not connect\n"); 61 exit(exit_failure); 62 } 63 64 freeaddrinfo(result); /* no longer needed */ 65 66 /* send remaining command-line arguments as separate 67 datagrams, and read responses from server */ 68 69 for (j = 3; j < argc; j++) { 70 len = strlen(argv[j]) + 1; 71 /* +1 for terminating null byte */ 72 73 if (len + 1 > buf_size) { 74 fprintf(stderr, 75 "ignoring long message in argument %d\n", j); 76 continue; 77 } 78 79 if (write(sfd, argv[j], len) != len) { 80 fprintf(stderr, "partial/failed write\n"); 81 exit(exit_failure); 82 } 83 84 nread = read(sfd, buf, buf_size); 85 if (nread == -1) { 86 perror("read"); 87 exit(exit_failure); 88 } 89 90 printf("received %zd bytes: %s\n", nread, buf); 91 } 92 93 exit(exit_success); 94 }
come from url: http://man7.org/linux/man-pages/man3/getaddrinfo.3.html
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