网络编程第三讲UDP编写

一丶UDP简介

　　UDP是面向无连接的.就是说数据传输会丢掉.网络延时比较大的情况下.会早上丢包.例如视频通话.就是UDP

UDP不需要建立建立. 下面有UDP编写流程图

下图为TCP 跟UDP的区别.

UDP下收发函数有区别.

　　发送数据: TCP: send UDP sendto

　　接受数据:TCP: recv UDP recvfrom

二丶UDP编写的完整代码

服务端:

#include <stdio.h>
#include <winsock2.h>
#include <Windows.h>
 
#pragma comment(lib,"ws2_32.lib")
#define  PORT 6000
 
int main(int argc, char* argv[])
{
    //初始化网络环境
    WSADATA wsa;
    if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)
    {
        printf("WSAStartup failed\n");
        return -1;
    }
 
    //建立一个UDP的socket
    SOCKET sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sock == SOCKET_ERROR)
    {
        printf("create socket failed\n");
        return -1;
    }
 
    //绑定地址信息
    sockaddr_in serverAddr;
    serverAddr.sin_family = AF_INET;
    serverAddr.sin_port = htons(PORT);
    serverAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);
 
    bind(sock, (sockaddr*)&serverAddr, sizeof(sockaddr));
    
    char buf[512];
    while (TRUE)
    {
        memset(buf, 0, 512);
        // 网络节点的信息，用来保存客户端的网络信息
        sockaddr_in clientAddr;
        memset(&clientAddr, 0, sizeof(sockaddr_in));
 
        int clientAddrLen = sizeof(sockaddr);
        //接收客户端发来的数据
        int ret = recvfrom(sock, buf, 512, 0,(sockaddr*) &clientAddr,&clientAddrLen );
        
        printf("Recv msg:%s from IP:[%s] Port:[%d]\n", buf,inet_ntoa(clientAddr.sin_addr),ntohs(clientAddr.sin_port));
        // 发一个数据包返回给客户
        sendto(sock, "Hello World!", strlen("Hello World!"), 0, (sockaddr*)&clientAddr, clientAddrLen);
        printf("Send msg back to IP:[%s] Port:[%d]\n", inet_ntoa(clientAddr.sin_addr), ntohs(clientAddr.sin_port));
    }
    return 0;
}

客户端

#include <stdio.h>
#include <winsock2.h>
#include <Windows.h>
 
#pragma comment(lib,"ws2_32.lib")
#define  PORT 6000
int main(int argc, char* argv[])
{
    //初始化网络环境
    WSADATA wsa;
    if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)
    {
        printf("WSAStartup failed\n");
        return -1;
    }
    //建立一个UDP的socket
    SOCKET sockClient = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sockClient == INVALID_SOCKET)
    {
        printf("create socket failed\n");
        return -1;
    }
    // 申明一个网络地址信息的结构体，保存服务器的地址信息
    sockaddr_in addr = { 0 };
    addr.sin_family = AF_INET;
    addr.sin_port = htons(PORT);
    addr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");
 
    char buf[] = "client test!";
    //发送数据
    int dwSent = sendto(sockClient, buf, strlen(buf), 0, (SOCKADDR *)&addr, sizeof(SOCKADDR));
    if (dwSent == 0)
    {
        printf("send %s failed\n", buf);
        return -1;
    }
    printf("send msg:%s\n", buf);
 
    char recvBuf[512];
    memset(recvBuf, 0, 512);
 
    sockaddr_in addrSever = { 0 };
    int nServerAddrLen=sizeof(sockaddr_in);
    // 接收数据
    int dwRecv = recvfrom(sockClient, recvBuf, 512, 0, (SOCKADDR *)&addrSever,&nServerAddrLen);
    printf("Recv msg from server : %s\n", recvBuf);
    //关闭SOCKET连接
    closesocket(sockClient);
    //清理网络环境
    WSACleanup();
    system("pause");
    return 0;
}