UDP-Socket一般流程（Windows）

一、 服務端構建步驟

1．初始化套接字環境WSAStartup
2．初始化地址和端口
3．創建UDP套接字socket
4．綁定端口bind
5．用recvfrom接收數據
6．用sendto發送數據
7．退出或者返回5步驟繼續

二、客戶端構建步驟

1.初始化套接字環境WSAStartup
2.初始化地址和端口
3.創建UDP套接字socket
4.用sendto發送數據
5.用recvfrom接收數據

三、示例代碼
Sever:

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

using namespace std;
int main()
{
	printf("server:\n");
	//1、初始化套接字環境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、創建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、綁定端口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接收數據
	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 接收數據出錯\n");
		}
		UINT uip = clientAddr.sin_addr.S_un.S_addr;
		printf("%s 來自於IP:%d.%d.%d,%d \n", buf, LOBYTE(uip), HIBYTE(uip), LOBYTE(HIWORD(uip)), HIBYTE(HIWORD(uip)));

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

		//7、退出或者返回第5步繼續
	}
	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、初始化套接字環境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、創建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發送數據
	while (1)
	{
		char sbuf[256] = {};
		cin.getline(sbuf, 256);
		sendto(client, sbuf, 256, 0, (sockaddr*)&serverAddr, sizeof(serverAddr));


		//5、用recvfrom接收數據
		int len = sizeof(clientAddr);
		char buf[256] = {};
		int r = recvfrom(client, buf, 256, 0, (sockaddr*)&clientAddr, &len);
		if (r == SOCKET_ERROR)
		{
			printf("client 接收數據出錯\n");
		}
		UINT uip = clientAddr.sin_addr.S_un.S_addr;
		printf("%s 來自於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步繼續
	}
	getchar();
	getchar();
	return 0;
}