Windows下的网络编程_windows网络编程

socket 接口已普遍存在于现代操作系统中

Windows 下的 socket 编程接口与 Linux 中几乎相同

不同之处

• 返回值类型不同 (句柄类型)
• 句柄不是文件描述符，Windows 中并不是一切皆文件

Windows 下 socket() 的用法

 Windows 网络编程接口

几点细微差异

通过 WSAStartup() 初始化系统环境 (最先调用)

socket()，accept() 错误返回 INVALID_SOCKET (不可默认为 -1)

bind()，listen() 错误返回 SOCKET_ERROR (不可默认为 -1)

connect()，send()，recv() 错误返回 SOCKET_ERROR (不可默认为 -1)

通过 WSACleanup() 清除系统环境 (最后调用)

Windows 网络编程的特殊说明

在工程属性中设置链接 ws2_32.lib

定义变量 WSADATA wd；

选择 socket 版本并初始化 WSAStartup(MAKEWORD(2，2)，&wd)；

• Windows 中存在多个 socket 版本

Windows 客户端编程示例

Windows 服务端编程示例

Windows 网络编程示例

client.c

 
#include <iostream>
#include <winsock2.h>
 
#pragma warning(disable : 4996)
 
int main()
{
	SOCKET sock = 0;
	struct sockaddr_in addr = { 0 };
	char input[32] = { 0 };
	char buf[128] = { 0 };
	int n = 0;
 
	WSADATA wd = { 0 };
 
	if (WSAStartup(MAKEWORD(2, 2), &wd) != 0)
	{
		printf("startup error\n");
 
		return -1;
	}
 
	sock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
 
	if (sock == INVALID_SOCKET)
	{
		printf("socker error\n");
 
		return -1;
	}
 
	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = inet_addr("127.0.0.1");
	addr.sin_port = htons(8888);
 
	if (connect(sock, (struct sockaddr*)&addr, sizeof(addr)) == SOCKET_ERROR)
	{
		printf("connect error\n");
 
		return -1;
	}
 
	printf("connect succeed\n");
 
	while (1)
	{
		printf("Input: ");
 
		scanf("%s", input);
 
		send(sock, input, strlen(input) + 1, 0);
 
		n = recv(sock, buf, sizeof(buf), 0);
 
		if (n > 0)
		{
			printf("Receive data: %s\n", buf);
		}
		else
		{
			break;
		}
	}
 
	closesocket(sock);
 
	WSACleanup();
 
	return 0;
}

server.c

 
#include <iostream>
#include <winsock2.h>
 
#pragma warning(disable : 4996)
 
int main()
{
	SOCKET server = 0;
	struct sockaddr_in saddr = { 0 };
	SOCKET client = 0;
	struct sockaddr_in caddr = { 0 };
	int csize = 0;
	char buf[32] = { 0 };
	int r = 0;
 
	WSADATA wd = { 0 };
 
	if (WSAStartup(MAKEWORD(2, 2), &wd) != 0)
	{
		printf("startup error\n");
 
		return -1;
	}
 
	server = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
 
	if (server == INVALID_SOCKET)
	{
		printf("server socket error\n");
 
		return -1;
	}
 
	saddr.sin_family = AF_INET;
	saddr.sin_addr.s_addr = htonl(INADDR_ANY);
	saddr.sin_port = htons(8888);
 
	if (bind(server, (struct sockaddr*)&saddr, sizeof(saddr)) == SOCKET_ERROR)
	{
		printf("server bind error\n");
 
		return -1;
	}
 
	if (listen(server, 1) == SOCKET_ERROR)
	{
		printf("server listen error\n");
 
		return -1;
	}
 
	printf("start to accept\n");
 
	while (1)
	{
		csize = sizeof(caddr);
 
		client = accept(server, (struct sockaddr*)&caddr, &csize);
 
		if (client == INVALID_SOCKET)
		{
			printf("server accept error\n");
 
			return -1;
		}
 
		printf("client = %d\n", client);
 
		do
		{
			r = recv(client, buf, sizeof(buf), 0);
 
			if (r > 0)
			{
				if (strcmp("quit", buf) == 0)
				{
					break;
				}
				else
				{
					printf("Receive data: %s\n", buf);
 
					send(client, buf, strlen(buf) + 1, 0);
				}
			}
 
		} while (r > 0);
 
		closesocket(client);
	}
 
	closesocket(server);
 
	WSACleanup();
 
	return 0;
}

程序运行结果如下：

问题

select() 是 Linux 系统特有的吗？

Windows 中的 select() 函数

Windows 中同样提供 select() 函数，且参数和 Linux 的版本完全相同

注意：Windows 中的 select() 函数，第一个参数没有任何意义 (仅为了兼容)

一个细微差异

Windows 中的 select() 专门为套接字而设计

• fd_count 用于记录感兴趣的 socket 数量
• fd_array 用于记录感兴趣的 socket 句柄值

Windows 中 select() 函数使用示例

Windows 中的多路复用服务端

 select-server.c

 
#include <iostream>
#include <winsock2.h>
 
#pragma warning(disable : 4996)
 
SOCKET server_handler(SOCKET server)
{
	struct sockaddr_in addr = { 0 };
	int asize = sizeof(addr);
 
	return accept(server, (struct sockaddr*)&addr, &asize);
}
 
int client_handler(SOCKET client)
{
	int ret = -1;
	char buf[32] = { 0 };
 
	ret = recv(client, buf, sizeof(buf) - 1, 0);
 
	printf("Receive: %s\n", buf);
 
	if (ret > 0)
	{
		buf[ret] = '0';
 
		if (strcmp(buf, "quit") != 0)
		{
			ret = send(client, buf, strlen(buf), 0);
		}
		else
		{
			ret = -1;
		}
	}
 
	return ret;
}
 
int main()
{
	SOCKET server = 0;
	struct sockaddr_in saddr = { 0 };
	int num = 0;
	fd_set reads = { 0 };
	fd_set temps = { 0 };
	struct timeval timeout = { 0 };
 
	WSADATA wd = { 0 };
 
	if (WSAStartup(MAKEWORD(2, 2), &wd) != 0)
	{
		printf("startup error\n");
 
		return -1;
	}
 
	server = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
 
	if (server == INVALID_SOCKET)
	{
		printf("server socket error\n");
 
		return -1;
	}
 
	saddr.sin_family = AF_INET;
	saddr.sin_addr.s_addr = htonl(INADDR_ANY);
	saddr.sin_port = htons(8888);
 
	if (bind(server, (struct sockaddr*)&saddr, sizeof(saddr)) == SOCKET_ERROR)
	{
		printf("server bind error\n");
 
		return -1;
	}
 
	if (listen(server, 1) == SOCKET_ERROR)
	{
		printf("server listen error\n");
 
		return -1;
	}
 
	FD_ZERO(&reads);
	FD_SET(server, &reads);
 
	printf("start to accept\n");
 
	while (1)
	{
		timeout.tv_sec = 0;
		timeout.tv_usec = 10000;
 
		temps = reads;
 
		num = select(0, &temps, NULL, NULL, &timeout);
 
		if (num > 0)
		{
			for (int i = 0; i <= reads.fd_count; i++)
			{
				SOCKET sock = reads.fd_array[i];
 
				if (FD_ISSET(sock, &temps))
				{
					if (sock == server)
					{
						SOCKET client = server_handler(server);
 
						if (client != INVALID_SOCKET)
						{
							FD_SET(client, &reads);
 
							printf("accept client: %d\n", client);
						}
					}
					else
					{
						if (client_handler(sock) == -1)
						{
							FD_CLR(sock, &reads);
 
							closesocket(sock);
						}
					}
				}
			}
		}
	}
 
	closesocket(server);
 
	WSACleanup();
 
	return 0;
}

Windows 下的 select() 函数，根据所监听文件描述符的个数遍历，相较于 Linux 的实现，遍历的次数更少，效率更高。

程序运行结果如下：

思考

 如何编写跨平台编译运行的网络程序？