WinSock学习笔记3：Select模型

最新推荐文章于 2021-12-15 13:16:53 发布

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最新推荐文章于 2021-12-15 13:16:53 发布

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分类专栏： Delphi（原创）文章标签： descriptor timer socket constructor button forms

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本文介绍了一种基于Select模型的Socket服务器实现方法，通过定时器接收客户端连接，并为每个连接创建独立线程进行消息接收处理。展示了如何利用Winsock API进行服务器端编程。

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unit Unit1; interface uses Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms, Dialogs, StdCtrls, WinSock, ExtCtrls; type TWorkThread = class(TThread) private FClientSocket: TSocket; FMemo: TMemo; FBuff: array [0..10] of Char; procedure ShowRecv; protected procedure Execute;override; public constructor Create(ClientSocket: TSocket; Memo: TMemo); end; TForm1 = class(TForm) Memo1: TMemo; Button1: TButton; Timer1: TTimer; procedure Button1Click(Sender: TObject); procedure Timer1Timer(Sender: TObject); private { Private declarations } public { Public declarations } end; var Form1: TForm1; ServerSocket: TSocket; ClientSocket: TSocket; implementation {$R *.dfm} procedure TForm1.Button1Click(Sender: TObject); var WSData: WSAData; LocalAddr: TSockAddrIn; SocketMode: Integer; begin //初始化Winsock WSAStartUp($202, WSData); //创建套接字 ServerSocket:= Socket(AF_INET, SOCK_STREAM, IPPROTO_TCP); //设置LocalAddr的参数 LocalAddr.sin_family:= AF_INET; //IPV4族 LocalAddr.sin_addr.S_addr:= Inet_addr('127.0.0.1');//点分字符串格式的IP地址转换为互联网格式 LocalAddr.sin_port:= Htons(1077); //Host To Net Short，主机字节顺序转为网络字节顺序 //绑定本机IP地址、端口，绑定之前先设置好LocalAddr的参数 Bind(ServerSocket, LocalAddr, SizeOf(LocalAddr)); //设置WinSock I/O模式 SocketMode:= 1; IoCtlSocket(ServerSocket, FIONBIO, SocketMode); //开始监听，最多同时监听5个连接 Listen(ServerSocket, 5); Timer1.Enabled:= True; end; { TWorkThread } constructor TWorkThread.Create(ClientSocket: TSocket; Memo: TMemo); begin inherited Create(False); FClientSocket:= ClientSocket; FMemo:= Memo; end; procedure TWorkThread.Execute; var FDSet: TFDSET; begin inherited; FreeOnTerminate:= True; while not Terminated do begin FD_Zero(FDSet); //初始化FDSet FD_SET(FClientSocket, FDSet); //将FClientSocket加入FDSet if Select(0, @FDSet, nil, nil, nil) > 0 then //测试FDSet中是否有可读的连接 begin if Recv(FClientSocket, FBuff, SizeOf(FBuff), 0) > 0 then //如果收到消息就显示出来 Synchronize(ShowRecv) else Break; end; end; end; procedure TWorkThread.ShowRecv; begin FMemo.Lines.Add(FBuff); end; procedure TForm1.Timer1Timer(Sender: TObject); begin ClientSocket:= Accept(ServerSocket, nil, nil); if ClientSocket <> INVALID_SOCKET then TWorkThread.Create(ClientSocket, Memo1); end; end.

1.使用Select模型，要定义一个FDSet结构，将客户端Socket加入该结构，用Select函数轮询测试该Socket的读写状态。FDSet结构：

    typedef struct fd_set {
    u_int fd_count;
      SOCKET fd_array[FD_SETSIZE];
    } fd_set;

2.操作FDSet结构有4个预定义的宏：

FD_CLR(s, *set)

Removes the descriptor s from set.

FD_ISSET(s, *set)

Nonzero if s is a member of the set. Otherwise, zero.

FD_SET(s, *set)

Adds descriptor s to set.

FD_ZERO(*set)

Initializes the set to the null set.

3.上面的代码为了方便，用了一个Timer来Accept，然后为每一个连接进来的Socket创建线程，在线程中用Select测试是否可读，为使代码简单，没有处理异常的代码。