UDP-Socket一般流程（Windows）

一、 服务端构建步骤

1．初始化套接字环境WSAStartup
2．初始化地址和端口
3．创建UDP套接字socket
4．绑定端口bind
5．用recvfrom接收数据
6．用sendto发送数据
7．退出或者返回5步骤继续

二、客户端构建步骤

1.初始化套接字环境WSAStartup
2.初始化地址和端口
3.创建UDP套接字socket
4.用sendto发送数据
5.用recvfrom接收数据

三、示例代码

Sever:

#include <winsock.h>
#include <stdio.h>
#include <iostream>
#pragma comment(lib, "ws2_32.lib")

using namespace std;
int main()
{
  printf("server:\n");
  //1、初始化套接字环境WSAStartup    
  WSADATA wsadata;
  int nError = WSAStartup(MAKEWORD(2, 2), &wsadata);
  if (nError != 0)
  {
    printf("初始化 ERROR\n");
    return -1;
  }

  //2、初始化地址和端口
  unsigned short CPORT = 6556;
  SOCKADDR_IN serverAddr, clientAddr;
  serverAddr.sin_family = AF_INET;
  serverAddr.sin_port = htons(CPORT);//端口
  serverAddr.sin_addr.S_un.S_addr = htonl(INADDR_ANY);//IP

  //3、创建UDP套接字socket  
  SOCKET server = socket(AF_INET, SOCK_DGRAM, 0);//make a socket
  if (server == INVALID_SOCKET)
  {
    printf("create socket failed!\n");
    closesocket(server);
    WSACleanup();
    return -1;
  }

  //4、绑定端口bind
  int retVal = bind(server, (sockaddr*)(&serverAddr), sizeof(serverAddr));//bind socket to address
  if (retVal == SOCKET_ERROR)
  {
    printf("bind failed!\n");
    closesocket(server);
    WSACleanup();
    return -1;
  }

  //5、用recvfrom接收数据
  int len = sizeof(clientAddr);
  while (1)
  {
    char buf[256] = {};
    int r = recvfrom(server, buf, 256, 0, (sockaddr*)&clientAddr, &len);
    if (r == SOCKET_ERROR)
    {
      printf("server 接收数据出错\n");
    }
    UINT uip = clientAddr.sin_addr.S_un.S_addr;
    printf("%s 来自于IP:%d.%d.%d,%d \n", buf, LOBYTE(uip), HIBYTE(uip), LOBYTE(HIWORD(uip)), HIBYTE(HIWORD(uip)));

    //6、用sendto发送数据
    char sbuf[256] = {};
    cin.getline(sbuf, 256);
    sendto(server, sbuf, 256, 0, (sockaddr*)&clientAddr, len);

    //7、退出或者返回第5步继续
  }
  getchar();
  getchar();
  return 0;
}

Client:

#include <winsock.h>
#include <stdio.h>
#include <iostream>
#pragma comment(lib, "ws2_32.lib")

using namespace std;
int main()
{
  printf("client:\n");
  //1、初始化套接字环境WSAStartup    
  WSADATA wsadata;
  int nError = WSAStartup(MAKEWORD(2, 2), &wsadata);
  if (nError != 0)
  {
    printf("初始化 ERROR\n");
    return -1;
  }

  //2、初始化地址和端口
  unsigned short CPORT = 6556;
  SOCKADDR_IN serverAddr, clientAddr;
  serverAddr.sin_family = AF_INET;
  serverAddr.sin_port = htons(CPORT);//端口
  serverAddr.sin_addr.S_un.S_addr = inet_addr("127.0.0.1");//IP

  //3、创建UDP套接字socket  
  SOCKET client = socket(AF_INET, SOCK_DGRAM, 0);//make a socket
  if (client == INVALID_SOCKET)
  {
    printf("create socket failed!\n");
    closesocket(client);
    WSACleanup();
    return -1;
  }

  //6、用sendto发送数据
  while (1)
  {
    char sbuf[256] = {};
    cin.getline(sbuf, 256);
    sendto(client, sbuf, 256, 0, (sockaddr*)&serverAddr, sizeof(serverAddr));


    //5、用recvfrom接收数据
    int len = sizeof(clientAddr);
    char buf[256] = {};
    int r = recvfrom(client, buf, 256, 0, (sockaddr*)&clientAddr, &len);
    if (r == SOCKET_ERROR)
    {
      printf("client 接收数据出错\n");
    }
    UINT uip = clientAddr.sin_addr.S_un.S_addr;
    printf("%s 来自于IP:%d.%d.%d,%d \n", buf, LOBYTE(uip), HIBYTE(uip), LOBYTE(HIWORD(uip)), HIBYTE(HIWORD(uip)));

    //7、退出或者返回第5步继续
  }
  getchar();
  getchar();
  return 0;
}