使用udp_client或者udp_connect和udp_server 的时间获取函数

udp_client.c函数代码：

/* include udp_client */

#include "unp.h"

int udp_client(const char *host, const char *serv, SA **saptr, socklen_t *lenp)
{
int
sockfd, n;
struct addrinfo
hints, *res, *ressave;

bzero(&hints,
sizeof(struct addrinfo));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;

if ( (n = getaddrinfo(host, serv, &hints, &res)) !=
0)

err_quit("udp_client error for %s, %s: %s",
host, serv, gai_strerror(n));
ressave = res;
do {
sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if (sockfd >=
0)

break;
/* success */
}
while ( (res = res->ai_next) !=
NULL);

if (res ==
NULL)
/* errno set from final socket() */

err_sys("udp_client error for %s, %s", host, serv);
*saptr = Malloc(res->ai_addrlen);
memcpy(*saptr, res->ai_addr, res->ai_addrlen);
*lenp = res->ai_addrlen;
freeaddrinfo(ressave);
return(sockfd);
}

/* end udp_client */

int Udp_client(const char *host, const char *serv, SA **saptr, socklen_t *lenptr)
{
return(udp_client(host, serv, saptr, lenptr));
}

daytimeupdcli1.c客户端代码：（使用udp_client.c）

#include "unp.h"

int main(int argc, char **argv)
{
int
sockfd, n;
char
recvline[MAXLINE + 1];
socklen_t
salen;
struct sockaddr
*sa;

if (argc !=
3)

err_quit("usage: daytimeudpcli1 <hostname/IPaddress> <service/port#>");

sockfd = Udp_client(argv[1], argv[2], (void
**) &sa, &salen);

printf("sending to %s\n", Sock_ntop_host(sa, salen));

Sendto(sockfd,
"", 1,
0, sa, salen); /* send 1-byte datagram */

n = Recvfrom(sockfd, recvline, MAXLINE,
0, NULL,
NULL);

recvline
=
'\0';
/* null terminate */
Fputs(recvline, stdout);

exit(0);
}

或者：
udp_connect.c代码：

/* include udp_connect */

#include "unp.h"

int udp_connect(const char *host, const char *serv)
{
int
sockfd, n;
struct addrinfo
hints, *res, *ressave;

bzero(&hints,
sizeof(struct addrinfo));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;

if ( (n = getaddrinfo(host, serv, &hints, &res)) !=
0)

err_quit("udp_connect error for %s, %s: %s",
host, serv, gai_strerror(n));
ressave = res;

do {
sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if (sockfd <
0)

continue;
/* ignore this one */

if (connect(sockfd, res->ai_addr, res->ai_addrlen) ==
0)

break;
/* success */

Close(sockfd);
/* ignore this one */
}
while ( (res = res->ai_next) !=
NULL);

if (res ==
NULL)
/* errno set from final connect() */

err_sys("udp_connect error for %s, %s", host, serv);
freeaddrinfo(ressave);
return(sockfd);
}

/* end udp_connect */

int Udp_connect(const char *host, const char *serv)
{
int
n;
if ( (n = udp_connect(host, serv)) <
0) {

err_quit("udp_connect error for %s, %s: %s",
host, serv, gai_strerror(-n));
}

return(n);
}

daytimeupdcli2.c（使用udp_connect.c）：

#include "unp.h"

int main(int argc, char **argv)
{
int
sockfd, n;
char
recvline[MAXLINE + 1];

if (argc !=
3)

err_quit("usage: daytimeudpcli2 <hostname/IPaddress> <service/port#>");

sockfd = Udp_connect(argv[1], argv[2]);

Write(sockfd,
"", 1);
/* send 1-byte datagram */

n = Read(sockfd, recvline, MAXLINE);

recvline
=
'\0';
/* null terminate */
Fputs(recvline, stdout);

exit(0);
}

udp_server.c代码：

/* include udp_server */

#include "unp.h"

int udp_server(const char *host, const char *serv, socklen_t *addrlenp)
{
int
sockfd, n;
struct addrinfo
hints, *res, *ressave;

bzero(&hints,
sizeof(struct addrinfo));
hints.ai_flags = AI_PASSIVE;
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_DGRAM;

if ( (n = getaddrinfo(host, serv, &hints, &res)) !=
0)

err_quit("udp_server error for %s, %s: %s",
host, serv, gai_strerror(n));
ressave = res;

do {
sockfd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if (sockfd <
0)

continue;
/* error - try next one */

if (bind(sockfd, res->ai_addr, res->ai_addrlen) ==
0)

break;
/* success */

Close(sockfd);
/* bind error - close and try next one */
}
while ( (res = res->ai_next) !=
NULL);

if (res ==
NULL)
/* errno from final socket() or bind() */

err_sys("udp_server error for %s, %s", host, serv);
if (addrlenp)

*addrlenp = res->ai_addrlen;
/* return size of protocol address */
freeaddrinfo(ressave);
return(sockfd);
}

/* end udp_server */

int Udp_server(const char *host, const char *serv, socklen_t *addrlenp)
{
return(udp_server(host, serv, addrlenp));
}

daitimeupdsrv2.c代码：

#include "unp.h"

#include <time.h>

int main(int argc, char **argv)
{
int
sockfd;
ssize_t
n;
char
buff[MAXLINE];
time_t
ticks;
socklen_t
len;
struct sockaddr_storage
cliaddr;

if (argc ==
2)
sockfd = Udp_server(NULL, argv[1],
NULL);
else
if (argc == 3)
sockfd = Udp_server(argv[1], argv[2],
NULL);

else

err_quit("usage: daytimeudpsrv [ <host> ] <service or port>");

for ( ; ; ) {
len =
sizeof(cliaddr);
n = Recvfrom(sockfd, buff, MAXLINE,
0, (SA *)&cliaddr, &len);
printf("datagram from %s\n", Sock_ntop((SA *)&cliaddr, len));

ticks = time(NULL);
snprintf(buff,
sizeof(buff), "%.24s\r\n", ctime(&ticks));
Sendto(sockfd, buff, strlen(buff),
0, (SA *)&cliaddr, len);
}
}

运行结果：
服务器：

➜ names ./daytimeudpsrv2 1399

datagram from 127.0.0.1:52995

datagram from 127.0.0.1:50425

客户端：

➜  names ./daytimeudpcli1 127.0.0.1 1399

sending to 127.0.0.1

Tue May  5 10:05:58 2015

➜  names ./daytimeudpcli2 127.0.0.1 1399

Tue May  5 10:06:04 2015