linux udp c/s

一、UDP C/S编程的步骤如下图所示

二、与TCP C/S通信的区别在于：
服务端没有设置监听和等待连接的过程。客户端没有连接服务端的过程。
基于UDP的通信时不可靠地，面向无连接的，发送的数据无法确切知道对方收到没有，就算对方根本不存在，也可以发送数据出去。
这样的通信通常用在对可靠性、安全性要求不高的地方，比如语音通信（没听清楚可以让对方再说一遍）。

三、server端编程

 #include <sys/types.h>

 #include <sys/socket.h>

 #include<pthread.h>

 #include <netinet/in.h>

 #include <stdio.h>

 #include <string.h>

 #include <unistd.h>

 #include <stdlib.h>

 int main(int argc, char **argv)

 {

     if (argc != )

     {

         printf("Usage: %s port\n", argv[]);

         exit();

     }

     printf("Welcome! This is a UDP server, I can only received message from client and reply with same message\n");

     struct sockaddr_in addr;   

     addr.sin_family = AF_INET;

     addr.sin_port = htons(atoi(argv[]));    //协商的发送端的端口号

     addr.sin_addr.s_addr = htonl(INADDR_ANY); //本机地址

     int sock;

     if ( (sock = socket(AF_INET, SOCK_DGRAM, )) < )

     {

         perror("socket");

         exit();

     }

     if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) < ) //绑定socket套接字到本地的监听端口

     {

         perror("bind");

         exit();

     }

     char buff[];

     struct sockaddr_in clientAddr;

     int n;

     int len = sizeof(clientAddr);

     while ()

     {

         n = recvfrom(sock, buff, , , (struct sockaddr*)&clientAddr, &len);//接收UDP包

         if (n>)

         {

             buff[n] = ;

             printf("%s %u says: %s\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port), buff);

             n = sendto(sock, buff, n, , (struct sockaddr *)&clientAddr, sizeof(clientAddr));//往发送方发送UDP回复包

             if (n < )

             {

                 perror("sendto");

                 break;

             }

         }

         else

         {

             perror("recv");

             break;

         }

     }

     return ;

 }

四、client端

 #include <sys/types.h>

 #include <sys/socket.h>

 #include<pthread.h>

 #include <netinet/in.h>

 #include <stdio.h>

 #include <string.h>

 #include <unistd.h>

 #include <stdlib.h>

 int main(int argc, char **argv)

 {

     if (argc != )

     {

         printf("Usage: %s ip port", argv[]);

         exit();

     }

     printf("This is a UDP client\n");

     struct sockaddr_in addr;

     int sock;

     if ( (sock=socket(AF_INET, SOCK_DGRAM, )) <)//创建socket

     {

         perror("socket");

         exit();

     }

     addr.sin_family = AF_INET;

     addr.sin_port = htons(atoi(argv[]));

     addr.sin_addr.s_addr = inet_addr(argv[]);//对方的IP地址、端口号

     if (addr.sin_addr.s_addr == INADDR_NONE)

     {

         printf("Incorrect ip address!");

         close(sock);

         exit();

     }

     char buff[];

     int len = sizeof(addr);

     while ()

     {

         gets(buff);

         int n;

         n = sendto(sock, buff, strlen(buff), , (struct sockaddr *)&addr, sizeof(addr));//往对方地址发送UDP包

         if (n < )

         {

             perror("sendto");

             close(sock);

             break;

         }

         n = recvfrom(sock, buff, , , (struct sockaddr *)&addr, &len);//接收来自对方IP地址的UDP包

         if (n>)

         {

             buff[n] = ;

             printf("received:");

             puts(buff);

         }

         else if (n==)

         {

             printf("server closed\n");

             close(sock);

             break;

         }

         else if (n == -)

         {

             perror("recvfrom");

             close(sock);

             break;

         }

     }

     return ;

 }

转自：http://www.cnblogs.com/uvsjoh/archive/2013/01/01/2841764.html

巴特西

linux udp c/s

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