Windows 网络通讯开发

一、Windows网络开发API

　　由于C++标准库中没有网络库，所以进行网络开发的时候要调用系统API。Windows通讯开发API包括以下几个基本函数及成员类型：

1. Header：Winsock.h 和 Winsock2.h（最新的）

具体Winsock2.h包含两大块内容：Socket Functions和Microsoft Windows-Specific Extension Functions

Socket Functions:

socket：An incoming connection is acknowledged and associated with an immediately created socket. The original socket is returned to the listening state.

SOCKET socket(int af,int type,int protocol);

bind：Assigns a local name to an unnamed socket.
listen：Listens for incoming connections on a specified socket.（一般在服务器端使用）
accept：An incoming connection is acknowledged（被确认） and associated with an immediately created socket. The original socket is returned to the listening state.（一般在服务器端使用）
connect：Initiates a connection on the specified socket.（一般在客户端使用）
send：Sends data to a connected socket.
sendto：Sends data to either a connected or unconnected socket.
recv：Receives data from a connected or unconnected socket.
recvfrom：Receives data from either a connected or unconnected socket.
htonl/htons/ntohl/ntohs：
h代表：host-byte；n代表：network-byte；l代表：32-bit；s代表：16-bit；
inet_addr：Converts a character string representing a number in the Internet standard ".'' notation to an Internet address value.
inet-ntoa：Converts an Internet address value to an ASCII string in ".'' notation that is, "a.b.c.d''.

Microsoft Windows-Specific Extension

Alt text

2. Library：Use Ws2_32.lib.

#pragma comment(lib, "ws2_32.lib")

3. 使用方法举例：

#include "stdafx.h"
#include <Winsock2.h>
#include <iostream>
using namespace std;
const int PORT = 10051;
int main(int argc, char* argv[])
{
	WSADATA wd;
	WSAStartup(0x202,&wd);
	SOCKET sock = socket(AF_INET,SOCK_STREAM,0);//侦听套接字
	if(sock == INVALID_SOCKET)
	{
		cout << "socket函数失败：" << WSAGetLastError() << endl;
		return -1;
	}
	sockaddr_in sa = {AF_INET,htons(PORT)};
	int n = bind(sock,(sockaddr*)&sa,sizeof(sa));
	if(n == SOCKET_ERROR)
	{
		cout << "bind函数失败：" << WSAGetLastError() << endl;
		return -1;
	}
	listen(sock,5);

	int nLen = sizeof(sa);
	SOCKET socka = accept(sock,(sockaddr*)&sa,&nLen);//如何循环等待多个客户端同时连接进来
	if(socka==INVALID_SOCKET)
	{
		cout << "accept函数失败：" << WSAGetLastError() << endl;
		return -1;
	}
	cout << "有人连接进来：" << inet_ntoa(sa.sin_addr) << "-" << htons (sa.sin_port)<< endl;
	char s[256];
	while((	n = recv(socka,s,sizeof(s)-1,0)) > 0)
	{
		s[n] = 0;
		cout << s << endl;
	}
	cout << WSAGetLastError() << endl;
	return 0;
}

详情参见：MSDN October 2001->Platform SDK: Windows Sockets

二、CAsyncSocket Class

定义：
Class CAsyncSocket encapsulates the Windows Socket Functions API, providing an object-oriented abstraction for programmers who want to use Windows Sockets in conjunction with MFC.
这个类封装了Window 套接字API，是比较底层的通讯类。
主要通讯流程：
To use a CAsyncSocket object, call its constructor, then call the Create function to create the underlying socket handle (type SOCKET), except on accepted sockets. For a server socket call the Listen member function, and for a client socket call the Connect member function. The server socket should call the Accept function upon receiving a connection request. Use the remaining CAsyncSocket functions to carry out communications between sockets. Upon completion, destroy the CAsyncSocket object if it was created on the heap; the destructor automatically calls the Close function. The SOCKET data type is described in the article Windows Sockets: Background.

详细使用情况参见Microsoft Help Veiwer 2.0

三、CSocket Class

Derives from CAsyncSocket and inherits its encapsulation of the Represents a higher level of abstraction of the Windows Sockets API than that of a CAsyncSocket object.
这个类是继承CAsyncSocket Class 的，它使用比其父类更加便捷。

详细使用情况参见Microsoft Help Veiwer 2.0