Linux UDP C/S例子

Linux UDP C/S例子

UDP C/S編程的步驟如下圖所示

與TCP C/S通信的區別在於：
服務端沒有設置監聽和等待連接的過程。客戶端沒有連接服務端的過程。
基於UDP的通信時不可靠地，面向無連接的，發送的數據無法確切知道對方收到沒有，就算對方根本不存在，也可以發送數據出去。
這樣的通信通常用在對可靠性、安全性要求不高的地方，比如語音通信（沒聽清楚可以讓對方再說一遍）。

#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 != 2)
    {
        printf("Usage: %s port\n", argv[0]);
        exit(1);
    }
    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[1]));
    addr.sin_addr.s_addr = htonl(INADDR_ANY);

    int sock;
    if ( (sock = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
    {
        perror("socket");
        exit(1);
    }
    if (bind(sock, (struct sockaddr *)&addr, sizeof(addr)) < 0)
    {
        perror("bind");
        exit(1);
    }
    char buff[512];
    struct sockaddr_in clientAddr;
    int n;
    int len = sizeof(clientAddr);
    while (1)
    {
        n = recvfrom(sock, buff, 511, 0, (struct sockaddr*)&clientAddr, &len);
        if (n>0)
        {
            buff[n] = 0;
            printf("%s %u says: %s\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port), buff);
            n = sendto(sock, buff, n, 0, (struct sockaddr *)&clientAddr, sizeof(clientAddr));
            if (n < 0)
            {
                perror("sendto");
                break;
            }
        }
        else
        {
            perror("recv");
            break;
        }
    }
    return 0;
}

#include<stdio.h>  
#include<stdlib.h>  
#include<string.h>  
#include<sys/socket.h>  
#include<sys/types.h>  
#include<unistd.h>  
#include<netinet/in.h>  
#include <errno.h>    

int main(int argc,char **argv)  
{  
    int sockfd;  
    int addrlen,n;  
    struct sockaddr_in addr_ser;  
    char recvline[200],sendline[200];  
      
    sockfd=socket(AF_INET,SOCK_DGRAM,0);  
    if(sockfd==-1)  
    {  
        printf("socket error:%s\n",strerror(errno));  
        return -1;  
    }  
      
    bzero(&addr_ser,sizeof(addr_ser));  
    addr_ser.sin_family=AF_INET;  
    addr_ser.sin_addr.s_addr=htonl(INADDR_ANY);  
    addr_ser.sin_port=htons(atoi(argv[1]));
      
    addrlen=sizeof(addr_ser);  
      
    while(1)  
    {  
        printf("Input your words: ");  
        scanf("%s",sendline);  
          
        n=sendto(sockfd,sendline,200,0,(struct sockaddr *)&addr_ser,addrlen);  
        if(n==-1)  
        {  
            printf("sendto error:%s\n",strerror(errno));  
            return -1;  
        }  
          
        printf("waiting for server......\n");  
        n=recvfrom(sockfd,recvline,200,0,(struct sockaddr *)&addr_ser,&addrlen);  
        if(n==-1)  
        {  
            printf("recvfrom error:%s\n",strerror(errno));  
            return -1;  
        }  
        recvline[n]='\0';  
        printf("recv data is:%s\n",recvline);  
    }  
      
    return 0;  
}