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Add example programs. 

Add getnameinfo() to SEE ALSO list.
This commit is contained in:
Michael Kerrisk 2007-05-28 10:30:10 +00:00
parent 77dbc3419e
commit 35bf3cc818
1 changed files with 209 additions and 2 deletions
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211
man3/getaddrinfo.3
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@ -1,4 +1,5 @@
.\" Copyright 2000 Sam Varshavchik <mrsam@courier-mta.com>
.\" and Copyright (c) 2007 Michael Kerrisk <mtk-manpages@gmx.net>
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
@ -24,8 +25,9 @@
.\"
.\" 2005-08-09, mtk, added AI_ALL, AI_ADDRCONFIG, AI_V4MAPPED,
.\" and AI_NUMERICSERV.
.\" 2007-06-08, mtk: added example programs
.\"
.TH GETADDRINFO 3 2000-12-18 "Linux" "Linux Programmer's Manual"
.TH GETADDRINFO 3 2007-06-08 "GNU" "Linux Programmer's Manual"
.SH NAME
getaddrinfo, freeaddrinfo, gai_strerror \- network address and service translation
.SH SYNOPSIS
@ -54,7 +56,8 @@ and
functions into a single interface.
The thread-safe
.BR getaddrinfo (3)
function creates one or more socket address structures that can be used by the
function creates one or more socket address structures
that can be used by the
.BR bind (2)
and
.BR connect (2)
@ -434,6 +437,210 @@ and
are available since glibc 2.3.3.
.BR AI_NUMERICSERV
is available since glibc 2.3.4.
.SH EXAMPLE
The following programs demonstrate the use of
.BR getaddrinfo (),
.BR gai_strerror (),
.BR freeaddrinfo (),
and
.BR getnameinfo (3).
The programs are an echo server and client for UDP datagrams.
This is the server:
.in +0.25i
.nf
#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/socket.h>
#include <netdb.h>
#define BUF_SIZE 500
int
main(int argc, char *argv[])
{
struct addrinfo hints;
struct addrinfo *result, *rp;
int sfd, s;
struct sockaddr_storage peer_addr;
socklen_t peer_addr_len;
ssize_t nread;
char buf[BUF_SIZE];
if (argc != 2) {
fprintf(stderr, "Usage: %s port\\n", argv[0]);
exit(EXIT_FAILURE);
}
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 = AI_PASSIVE; /* For wildcard IP address */
hints.ai_protocol = 0; /* Any protocol */
s = getaddrinfo(NULL, argv[1], &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 bind().
If socket() (or bind()) 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 (bind(sfd, rp->ai_addr, rp->ai_addrlen) == 0)
break; /* Success */
close(sfd);
}
if (rp == NULL) { /* No address succeeded */
fprintf(stderr, "Could not bind\\n");
exit(EXIT_FAILURE);
}
freeaddrinfo(result); /* No longer needed */
/* Read datagrams and echo them back to sender */
for (;;) {
peer_addr_len = sizeof(struct sockaddr_storage);
nread = recvfrom(sfd, buf, BUF_SIZE, 0,
(struct sockaddr *) &peer_addr, &peer_addr_len);
if (nread == -1)
continue; /* Ignore failed request */
char host[NI_MAXHOST], service[NI_MAXSERV];
s = getnameinfo((struct sockaddr *) &peer_addr,
peer_addr_len, host, NI_MAXHOST,
service, NI_MAXSERV, NI_NUMERICSERV);
if (s == 0)
printf("Received %ld bytes from %s:%s\\n",
(long) nread, host, service);
else
fprintf(stderr, "getnameinfo: %s\\n", gai_strerror(s));
if (sendto(sfd, buf, nread, 0,
(struct sockaddr *) &peer_addr,
peer_addr_len) != nread)
fprintf(stderr, "Error sending response\\n");
}
}
.fi
.in
This is the client:
.in +0.25i
.nf
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#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().
If socket() (or connect()) 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);
}
.fi
.in
.SH "SEE ALSO"
.BR getipnodebyaddr (3),
.BR getipnodebyname (3)
.BR getnameinfo (3),