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;
}