关于select

[z75050429]

// MUD Programming
// Ron Penton
// (C)2003
// Demo02-03.cpp - Hello Internet! Server v2
// This program will start up a server on port 4000, listen for connections,
// receive data until the other side quits, and then close the connection, and
// wait for more data; all the while simulation other game functions.


// Code Block 2.1 - Header Includes
// This code block includes all of the standard Sockets API/Winsock headers
#ifdef WIN32 // windows 95 and above
#include "winsock2.h"
#include "Ws2tcpip.h"

#else // UNIX/Linux
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#include <netdb.h>
#include <arpa/inet.h>
#endif
// End Code Block 2.1 - Header Includes



// Code Block 2.2 - Redefinitions and globals For Cross-Compatibility
#ifdef WIN32 // windows 95 and above
WSADATA g_wsadata; // winsock data holder
#define CloseSocket closesocket
#define GetSocketError WSAGetLastError
#define StartSocketLib WSAStartup( MAKEWORD( 2, 2 ), &g_wsadata );
#define CloseSocketLib WSACleanup();

#ifndef socklen_t
typedef int socklen_t;
#endif
#else // Unix/Linux
#define CloseSocket close
#define GetSocketError errno
#define StartSocketLib {}
#define CloseSocketLib {}
#endif

// End Code Block 2.2 - Redefinitions and globals For Cross-Compatibility



#include <iostream> // load the iostream library
#include <vector>
#include <string.h> // for string manipulations
using namespace std; // use the std namespace


int main()
{
int err; // for getting errors
int lsock; // listening socket
vector<int> socketlist; // list of sockets

// start the socket library
StartSocketLib;

// BEGIN CODE BLOCK 2.3 - Create a Listening Socket on port 4000
// create a socket
lsock = socket( AF_INET, SOCK_STREAM, IPPROTO_TCP );

// check if socket was created
if( lsock == -1 )
{
cout << "Socket creation error!" << endl;
return 0;
}
cout << "Socket created!" << endl;

// create a sockaddr_in for binding, listening on port 4000
struct sockaddr_in socketaddress;
socklen_t sa_size = sizeof( struct sockaddr_in );
socketaddress.sin_family = AF_INET;
socketaddress.sin_port = htons( 4000 );
socketaddress.sin_addr.s_addr = htonl( INADDR_ANY );
memset( &(socketaddress.sin_zero), 0, 8 );

// bind the socket
err = bind( lsock, (struct sockaddr*)&socketaddress, sa_size );

if( err == -1 )
{
cout << "Socket binding error!" << endl;
return 0;
}
cout << "Socket bound!" << endl;


// listen on the socket
err = listen( lsock, 16 );

if( err == -1 )
{
cout << "Socket listening error!" << endl;
return 0;
}
cout << "Socket listening, waiting for connection..." << endl;
// END CODE BLOCK 2.3 - Create a Listening Socket on port 4000


fd_set rset;
int i;

struct timeval zerotime;
zerotime.tv_usec = 0;
zerotime.tv_sec = 0;

char buffer[128]; // used for getting messages
bool done = false; // used for quitting
vector<int>::iterator itr;

// now begin the main loop.
while( !done )
{
// clear the set
FD_ZERO( &rset );

// add the listening socket
FD_SET( lsock, &rset );

// add all of the data sockets
for( itr = socketlist.begin(); itr != socketlist.end(); itr++ )
{
FD_SET( *itr, &rset );
}

// find out if there is any activity on any of the sockets.
i = select( 128, &rset, NULL, NULL, &zerotime );

if( i > 0 )
{
if( FD_ISSET( lsock, &rset ) )
{
// incomming connection
cout << "Incomming connection..." << endl;
int dsock = accept( lsock,
(struct sockaddr*)&socketaddress,
&sa_size );
if( dsock == -1 )
{
cout << "Socket accepting error!" << endl;
return 0;
}
cout << "Socket " << dsock << " accepted." << endl;

// add the socket to the list
socketlist.push_back( dsock );
}

// loop through each socket and see if it has any activity
for( itr = socketlist.begin(); itr != socketlist.end(); itr++ )
{
if( FD_ISSET( *itr, &rset ) )
{
// incomming data
cout << "receiving data from socket ";
cout << *itr << "..." << endl;
err = recv( *itr, buffer, 128, 0 );

if( err == -1 )
{
cout << "Socket receiving error!" << endl;
return 0;
}
if( err == 0 )
{
cout << "Socket " << *itr << " closed" << endl;
shutdown( *itr, 2 );
CloseSocket( *itr );
socketlist.erase( itr );
itr--;
}
else
{

cout << "Data: " << buffer << endl;

// if the message was "servquit", then quit the server.
if( strcmp( buffer, "servquit" ) == 0 )
done = true;
}
}
}
}

}


shutdown( lsock, 2 );
CloseSocket( lsock );

for( i = 0; i < socketlist.size(); i++ )
{
shutdown( socketlist[i], 2 );
CloseSocket( socketlist[i] );
}

CloseSocketLib;
}
while( !done )内的请解释下下··谢谢

[gccli]

// now begin the main loop.
while( !done )
{
// clear the set
FD_ZERO( &rset ); //读集，表示监视有没有准备好的可读文件描述符，此时这个集合中为空

// add the listening socket
FD_SET( lsock, &rset ); //添加lsock这个Socket描述符到这个(rset)集合中

// add all of the data sockets
for( itr = socketlist.begin(); itr != socketlist.end(); itr++ )
{
FD_SET( *itr, &rset ); //添加socketlist列表中的Socket描述符到这个(rset)集合中
}

// find out if there is any activity on any of the sockets.
i = select( 128, &rset, NULL, NULL, &zerotime ); //这里会进行阻塞（这么长时间zerotime），直到上面集合中有一个文件描述符中准备好了数据

if( i > 0 ) //i>0表示有i个文件描述符准备好了数据
{
if( FD_ISSET( lsock, &rset ) ) //先判断这个准备好数据的描述符是不是lscok
{
// incomming connection //从这里可以看出这个lsock是用来监听连接用的，如果有连接则将连接的客户端的socket放入socketlist中
cout < < "Incomming connection..." < < endl;
int dsock = accept( lsock, //客户端连接后的socket
(struct sockaddr*)&socketaddress,
&sa_size );
if( dsock == -1 )
{
cout < < "Socket accepting error!" < < endl;
return 0;
}
cout < < "Socket " < < dsock < < " accepted." < < endl;

// add the socket to the list
socketlist.push_back( dsock );
}

// loop through each socket and see if it has any activity
for( itr = socketlist.begin(); itr != socketlist.end(); itr++ )
{ //从这里可以看出，socketlist中的描述是用来接收数据的
//这里是轮询这些socket，如果在linux下，我建议不要用select效率太低，建议用epoll
if( FD_ISSET( *itr, &rset ) )
{
// incomming data
cout < < "receiving data from socket ";
cout < < *itr < < "..." < < endl;
err = recv( *itr, buffer, 128, 0 ); //接收数据，如果接收到servquit则客户端要要服务器退出
// 看到这里，我不得不说，此程序效率差且结构不合理

if( err == -1 )
{
cout < < "Socket receiving error!" < < endl;
return 0;
}
if( err == 0 )
{
cout < < "Socket " < < *itr < < " closed" < < endl;
shutdown( *itr, 2 );
CloseSocket( *itr );
socketlist.erase( itr );
itr--;
}
else
{

cout < < "Data: " < < buffer < < endl;

// if the message was "servquit", then quit the server.
if( strcmp( buffer, "servquit" ) == 0 )
done = true;
}
}
}
}

}

[scott_1987]

好长，新手刚学！心有力而力不足啊！

[SearchLife]

好长啊,mmk

[hhyttppd]

// now begin the main loop. 
while( !done )                                                         //查看__{Quit}__处
{ 
	// clear the set 
	FD_ZERO( &rset ); 

	// add the listening socket 
	FD_SET( lsock, &rset ); 

	// add all of the data sockets 
	for( itr = socketlist.begin(); itr != socketlist.end(); itr++ ) 
	{ 
		FD_SET( *itr, &rset ); 
	} 

	// find out if there is any activity on any of the sockets. 
	i = select( 128, &rset, NULL, NULL, &zerotime );                    //用MSDN查看select的说明，此处一直等待，直到rset句柄集中有输入
	                                                                    //这个集包括连接处理套接字和所accept的套接字
	                                                                    //lsock如果有输入则说明有新的连接请求
	                                                                    

	if( i > 0 ) 
	{ 
		if( FD_ISSET( lsock, &rset ) )                                    //有新连接
		{ 
			// incomming connection 
			cout < < "Incomming connection..." < < endl; 
			int dsock = accept( lsock,                                      //响应并建立新连接
				(struct sockaddr*)&socketaddress, 
				&sa_size ); 
			if( dsock == -1 ) 
			{ 
				cout < < "Socket accepting error!" < < endl; 
				return 0; 
			} 
			cout < < "Socket " < < dsock < < " accepted." < < endl; 

			// add the socket to the list 
			socketlist.push_back( dsock );                                   //保存
		} 

		// loop through each socket and see if it has any activity 
		for( itr = socketlist.begin(); itr != socketlist.end(); itr++ ) 
		{ 
			if( FD_ISSET( *itr, &rset ) )                                    //遍历，看某个连接是否有新的输入数据
			{ 
				// incomming data 
				cout < < "receiving data from socket "; 
				cout < < *itr < < "..." < < endl; 
				err = recv( *itr, buffer, 128, 0 ); 

				if( err == -1 ) 
				{ 
					cout < < "Socket receiving error!" < < endl; 
					return 0; 
				} 
				if( err == 0 ) 
				{ 
					cout < < "Socket " < < *itr < < " closed" < < endl; 
					shutdown( *itr, 2 ); 
					CloseSocket( *itr ); 
					socketlist.erase( itr ); 
					itr--; 
				} 
				else 
				{ 

					cout < < "Data: " < < buffer < < endl; 

					// if the message was "servquit", then quit the server. 
					if( strcmp( buffer, "servquit" ) == 0 )                             //__{Quit}__---------退出客户端发来的servquit消息，则服务退出
						done = true; 
				} 
			} 
		} 
	} 

} 

[bitwwzhang130]

太长了,慢慢看

[太乙]

upup

[星羽]

so long

[hityct1]

不是有英语注释了吗？

[lq20051610211]

oh, my god~

[artwl_cn]

帮顶！

[就呆在云上]

建议你去看看unix环境高级编程里面说的非常的清楚了
select的使用
他获取等待的文件描述符，得到后返回
超时返回
等等

[caremsi]

FD_ZERO( &rset ); //把rset这个文件描述符集置0
// add the listening socket
FD_SET( lsock, &rset ); //添加lsock到rset这个文件描述符集

// add all of the data sockets
for( itr = socketlist.begin(); itr != socketlist.end(); itr++ )
{
FD_SET( *itr, &rset ); //同上
}

// find out if there is any activity on any of the sockets.
i = select( 128, &rset, NULL, NULL, &zerotime ); //select我的理解类似于激活开始判断文件描述集的状况

if( i > 0 )
{
if( FD_ISSET( lsock, &rset ) ) //当lsock有变化,则进入到if里的继续

[rabbii]

[Quote=引用 12 楼 scott_1987 的回复:]
好长，新手刚学！心有力而力不足啊！
[/Quote]
up~~~