一、实现的过程

//无连接、不可靠、尽最大的努力发出去，不保证能收到，效率高

UDP：视频传输，eg:打视频电话,处理丢包的成本很低；

二、代码：

1.ser.c

#include<stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <assert.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main()
{
    int sockfd=socket(AF_INET,SOCK_DGRAM,0);
    if(sockfd==-1)
    {   
        exit(0);
    }   

    struct sockaddr_in saddr,caddr;
    memset(&saddr,0,sizeof(saddr));
    saddr.sin_family=AF_INET;
    saddr.sin_port=htons(6000);
    saddr.sin_addr.s_addr=inet_addr("127.0.0.1");

    int res=bind(sockfd,(struct sockaddr*)&saddr,sizeof(saddr));

    while(1)
    {   
        int len=sizeof(caddr);
        char buff[128]={0};
        int n=recvfrom(sockfd,buff,127,0,(struct sockaddr*)&caddr,&len);
        printf("ip:%s,buff=%s\n",inet_ntoa(caddr.sin_addr),buff);
        sendto(sockfd,"ok",2,0,(struct sockaddr*)&caddr,sizeof(caddr));
    }   
}

2.cli.c

#include<stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <assert.h>
#include <sys/socket.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main()
{
    int sockfd=socket(AF_INET,SOCK_DGRAM,0);
    if(sockfd==-1)
    {
        exit(0);
    }

    struct sockaddr_in saddr,caddr;
    memset(&saddr,0,sizeof(saddr));
    saddr.sin_family=AF_INET;
    saddr.sin_port=htons(6000);
    saddr.sin_addr.s_addr=inet_addr("127.0.0.1");

    int res=bind(sockfd,(struct sockaddr*)&saddr,sizeof(saddr));

    while(1)
    {
        int len=sizeof(caddr);
        char buff[128]={0};
        int n=recvfrom(sockfd,buff,127,0,(struct sockaddr*)&caddr,&len);
        printf("ip:%s,buff=%s\n",inet_ntoa(caddr.sin_addr),buff);
        sendto(sockfd,"ok",2,0,(struct sockaddr*)&caddr,sizeof(caddr));
    }
}