TCP/IP网络编程学习之路二

基于Windows下的网络编程：

网络编程基本上都有服务器端和客户端，这两个端所实现的方法是不一样的。

服务器端的一般框架

1. 用socket()函数创建一个套接字，并建立资源所使用的资源 SOCKET socket(int af,int type,int protocol) 
2. 用bind()函数绑定套接字，并为其分配IP 地址和端口号 int PASCAL FAR bind( SOCKET s,const struct sockaddr FAR *name,int namelen )
3. 用listen()函数监听是否有客户端想连接 int PASCAL FAR listen( SOCKET s, int backlog )
4. 用accept()函数来接收客户端的连接请求， 同时创建一个新的套接字来和客户端通信    SOCKET PASCAL FAR accept(SCOKET s,struct sockaddr FAR *addr,int FAR *addrlen);

客户端的一般框架

1. 用socket()函数创建一个套接字，并建立资源所使用的资源 SOCKET socket(int af,int type,int protocol) 
2. 用connect()函数来连接服务器int PASCAL FAR connect( SOCKET s,const struct sockaddr FAR *name,int namelen );

只有我们写完这些步骤，服务器和客户端才有可能联通，【注意】服务器通过accept()生成的套接字和客户端生成的套接字来通信！

接下来解释函数参数的意思

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

af 表示套接字中使用的协议族信息， type表示套接字的类型（面向连接的或者面向无连接的），protocol表示计算机间通信中使用的协议信息（一般写0）；

int PASCAL FAR bind( SOCKET s,const struct sockaddr FAR *name,int namelen );

s 是socket()函数创建的套接字 name 是Socket的位址值，其格式为 struct sockaddr { u_short sa_family; char sa_data[14]; }; namelen 是name的长度

int PASCAL FAR listen( SOCKET s, int backlog );

s是socket（）函数创建的套接字， backlog是最多允许的连接数。

SOCKET PASCAL FAR accept(SCOKET s,struct sockaddr FAR *addr,int FAR *addrlen);

s 是socket（）函数创建的套接字， addr 存放来连接的彼端的位址； addrlen addr的长度，这个函数会返回新的套接字！

int PASCAL FAR connect( SOCKET s,const struct sockaddr FAR *name,int namelen );

s是客户端通过socket（）函数创建的套接字，name 是此 Socket 想要连接的对方位址 namelen 是name的长度；

服务器的基本框架

#include <iostream>
#include <WinSock2.h>
#include <cstdlib>
#include <cstring>

#pragma comment(lib, "ws2_32.lib")
using namespace std;
const int MAXLENGTH = 4096;



int main()
{
	WSADATA wsaData;
	int result = WSAStartup(MAKEWORD(2,2), &wsaData);
	if(result != NO_ERROR)
	{
		cerr << "init winsock failured" << endl;
		exit(1);
	}

	SOCKET serversocket;

	serversocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if(serversocket == INVALID_SOCKET)
	{
		cout << "建立socket失败" << WSAGetLastError() << endl;
		system("pause");
		return -1;
	}

	sockaddr_in server;
	server.sin_family = AF_INET;
	server.sin_addr.s_addr = inet_addr("127.0.0.1");
	server.sin_port = htons(6800);

	result = bind(serversocket, (struct sockaddr *)&server, sizeof(server));
	if(result == SOCKET_ERROR)
	{
		cout << "绑定失败" << endl;
		system("pause");
		return -1;
	}

	result = listen(serversocket, 5);
	if(result == SOCKET_ERROR)
	{
		cout << "监听失败" << endl;
		system("pause");
		return -1;
	}

	char recvbuf[1024];
	struct sockaddr_in client;
	int length =sizeof(client);
	SOCKET acceptsock = accept(serversocket, (struct sockaddr *)&client, &length);
	if(acceptsock == INVALID_SOCKET)
	{
		cout << "接受失败" << endl;
		system("pause");
		return -1;
	}

	result = recv(acceptsock, recvbuf, strlen(recvbuf), 0);
	if(result == SOCKET_ERROR)
	{
		cout << "接收失败" << endl;
		system("pause");
		return -1;
	}
	
	cout << recvbuf << endl;
	cin >> recvbuf;
	result = send(acceptsock, recvbuf, strlen(recvbuf), 0);
	if(result == SOCKET_ERROR)
	{
		cout << "发送失败" << endl;
		system("pause");
		return -1;
	}
	
	closesocket(acceptsock);
	closesocket(serversocket);
	WSACleanup();

	system("pause");
	return 0;
}

客户端的基本框架

#include <iostream>
#include <WinSock2.h>
#include <cstring>

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

using namespace std;

int main()
{
	WSADATA wsaData;
	int ret = WSAStartup(MAKEWORD(2,2), &wsaData);
	if(ret != 0)
	{
		cout << "初始化win失败"  << endl;
		system("pause");
		return -1;
	}

	SOCKET clientsocket;
	clientsocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if(clientsocket == SOCKET_ERROR)
	{
		cout << "创建socket失败" << endl;
		system("pause");
		return -1;
	}

	struct sockaddr_in server;
	server.sin_family = AF_INET;
	server.sin_addr.s_addr = inet_addr("127.0.0.1");
	server.sin_port = htons(6800);

	ret = connect(clientsocket, (struct sockaddr *)&server, sizeof(server));
	if(ret == SOCKET_ERROR)
	{
		cout << "连接失败" << GetLastError() << endl;
		system("pause");
		return -1;
	}

	char buffer[1024];
	cin >> buffer;
	ret = send(clientsocket, buffer, strlen(buffer), 0);
	if(ret == SOCKET_ERROR)
	{
		cout << "发送失败" << GetLastError() << endl;
		system("pause");
		return -1;
	}
	ret = recv(clientsocket, buffer, strlen(buffer), 0);
	if(ret == SOCKET_ERROR)
	{
		cout << "接收失败" << GetLastError() << endl;
		system("pause");
		return -1;
	}
	cout << buffer << endl;

	closesocket(clientsocket);
	WSACleanup();
	system("pause");
	return 0;
}