Linux网络编程之---UDP

一.UDP通信流程

1.server:
    1.创建一个socket()
    2.bind()
    3.recvfrom()
    4.sendto()
    5.close()

2.client:
    1.socket
    2.sendto()
    3.recvfrom()
    4.close()

 二.涉及到的api

ssize_t sendto(int sockfd, const void *buf, size_t len, int flags,
                      const struct sockaddr *dest_addr, socklen_t addrlen);

    -参数:
        - sockfd : 通信的fd
        - buf : 要发送的数据
        - len : 发送数据的长度
        - flags : 0
        - dest_addr : 通信的另外一端的地址信息
        - addrlen : 地址的内存大小
    
ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags,
                        struct sockaddr *src_addr, socklen_t *addrlen);
    -参数:
        -sockfd:通信的fd
        -buf:接收数据的数组
        -len:数组的大小
        -flags:0
        -src_addr : 用来保存另外一段的地址信息，不需要指定为NULL
        -socklen_t:地址的内存大小

 三.udp服务端和客户端代码实现

 1.服务端

 

#include <stdio.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>int main()
{int udp_sockfd = socket(AF_INET,SOCK_DGRAM,0);if(udp_sockfd == -1){perror("socket");exit(-1);}struct sockaddr_in server;server.sin_family = AF_INET;server.sin_addr.s_addr = INADDR_ANY;server.sin_port = htons(8000);int opt = 1;setsockopt(udp_sockfd,SOL_SOCKET,SO_REUSEPORT,(const void*)&opt,sizeof(opt));if(bind(udp_sockfd,(const struct sockaddr*)&server,sizeof(server)) == -1){perror("bind");exit(-1);}char recvbuff[1024];struct sockaddr_in clienaddr;int len = sizeof(clienaddr);char client_ip[16] = {0};unsigned int client_port = 0;while(1){memset(recvbuff,0,sizeof(recvbuff));//接收数据int num = recvfrom(udp_sockfd,recvbuff,sizeof(recvbuff),0,(struct sockaddr*)&clienaddr,&len);if(num == -1){perror("recvfrom");exit(-1);}printf("recv data:%s,client ip : %s, client port : %d\n",recvbuff,inet_ntop(AF_INET,(const void*)&clienaddr.sin_addr.s_addr,client_ip,sizeof(client_ip)),ntohs(clienaddr.sin_port));//发送数据sendto(udp_sockfd,recvbuff,strlen(recvbuff)+1,0,(const struct sockaddr*)&clienaddr,sizeof(clienaddr));}close(udp_sockfd);return 0;
}

2.客户端

#include <stdio.h>
#include <arpa/inet.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>int main()
{int udp_sockfd = socket(AF_INET,SOCK_DGRAM,0);if(udp_sockfd == -1){perror("socket");exit(-1);}char recvbuff[1024];char *sendbuf;//服务器地址信息struct sockaddr_in saddr;saddr.sin_family = AF_INET;saddr.sin_addr.s_addr = inet_addr("127.0.0.1");saddr.sin_port = htons(8000);int len = sizeof(saddr);while(1){printf("亲爱的用户，请您输入你想要发送给服务器的信息:");scanf("%s",sendbuf);//发送数据sendto(udp_sockfd,sendbuf,strlen(sendbuf)+1,0,(const struct sockaddr*)&saddr,sizeof(saddr));memset(recvbuff,0,sizeof(recvbuff));//接收数据int num = recvfrom(udp_sockfd,recvbuff,sizeof(recvbuff),0,NULL,NULL);if(num == -1){perror("recvfrom");exit(-1);}printf("接收到回射信息:%s\n",recvbuff);}close(udp_sockfd);return 0;
}