距离详解Linux下的UDP方式通讯

UDP方式点对点通讯 

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main(int argc, char **argv)
{
struct sockaddr_in s_addr;
struct sockaddr_in c_addr;
int sock;
socklen_t addr_len;
int len;
char buff[128];


if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(errno);
} else
printf("create socket.nr");

memset(&s_addr, 0, sizeof(struct sockaddr_in));

s_addr.sin_family = AF_INET;
if (argv[2])
s_addr.sin_port = htons(atoi(argv[2]));
else
s_addr.sin_port = htons(7838);
if (argv[1])
s_addr.sin_addr.s_addr = inet_addr(argv[1]);
else
s_addr.sin_addr.s_addr = INADDR_ANY;


if ((bind(sock, (struct sockaddr *) &s_addr, sizeof(s_addr))) == -1) {
perror("bind");
exit(errno);
} else
printf("bind address to socket.nr");


addr_len = sizeof(c_addr);
while (1) {
len = recvfrom(sock, buff, sizeof(buff) - 1, 0,
(struct sockaddr *) &c_addr, &addr_len);
if (len < 0) {
perror("recvfrom");
exit(errno);
}

buff[len] = '';
printf("收到来自%s:%d的消息:%snr",
inet_ntoa(c_addr.sin_addr), ntohs(c_addr.sin_port), buff);
}
return 0;
}

客户端源代码如下：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 


int main(int argc, char **argv)
{
struct sockaddr_in s_addr;
int sock;
int addr_len;
int len;
char buff[128];


if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(errno);
} else
printf("create socket.nr");


s_addr.sin_family = AF_INET;
if (argv[2])
s_addr.sin_port = htons(atoi(argv[2]));
else
s_addr.sin_port = htons(7838);
if (argv[1])
s_addr.sin_addr.s_addr = inet_addr(argv[1]);
else {
printf("消息必须有一个接收者！n");
exit(0);
}


addr_len = sizeof(s_addr);
strcpy(buff, "hello i'm here");
len = sendto(sock, buff, strlen(buff), 0,
(struct sockaddr *) &s_addr, addr_len);
if (len < 0) {
printf("nrsend error.nr");
return 3;
}

printf("send success.nr");
return 0;
}

编译程序用下列命令：

gcc -Wall simple-udpserver.c -o server
gcc -Wall simple-udpclient.c -o client

运行程序用下列命令：

./server 127.0.0.1 7838

./client 127.0.0.1 7838

UDP方式广播通讯 
源代码变成下面的：

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

int main(int argc, char **argv)
{
struct sockaddr_in s_addr;
int sock;
int addr_len;
int len;
char buff[128];
int yes;


if ((sock = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket");
exit(errno);
} else
printf("create socket.nr");


yes = 1;
setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &yes, sizeof(yes));



s_addr.sin_family = AF_INET;
if (argv[2])
s_addr.sin_port = htons(atoi(argv[2]));
else
s_addr.sin_port = htons(7838);
if (argv[1])
s_addr.sin_addr.s_addr = inet_addr(argv[1]);
else {
printf("消息必须有一个接收者！n");
exit(0);
}


addr_len = sizeof(s_addr);
strcpy(buff, "hello i'm here");
len = sendto(sock, buff, strlen(buff), 0,
(struct sockaddr *) &s_addr, addr_len);
if (len < 0) {
printf("nrsend error.nr");
return 3;
}

printf("send success.nr");
return 0;
}

编译这个程序用下列命令：

gcc -Wall broadc-udpclient.c -o client

运行程序用下列命令：

./client 192.168.0.255 7838

就会往192.168.0网络内所有主机发消息。

其它主机如果运行了服务端：

./server 自己的IP地址 7838

则都会收到上述客户端发的消息了。