客户端与服务器端编程

A. TCP服务器和客户机编程

服务器（TCP/IP）编程实例
现在大多数语言都支持客户－服务器模式(C/S)编程，其中VB给我们提供了很好的客户－服务器编程方式。下面我们用VB来实现TCP／IP网络编程。
TCP／IP协议是Internet最重要的协议。VB提供了WinSock控件,用于在TCP／IP的基础上进行网络通信。当两个应用程序使用Socket进行网络通信时，其中一个必须创建Socket服务器侦听，而另一个必须创建Socket客户去连接服务器。这样两个程序就可以进行通信了。
①创建服务器
首先创建一个服务端口号。并开始侦听是否有客户请求连接。
建立一窗体，并向其增加一个Winsock控件(可在工程菜单中的部件项来添加此控件)
添加两文本框Text1,Text2,和一按钮Command1
Private Sub Form_Load()
SockServer.LocalPort = 2000 ′服务器端口号,最好大于1000
SockServer.Listen ′开始侦听
End Sub
Private Sub Form_Unload(Cancel As Integer)
SockServer.Close
End Sub
Private Sub SockServer_Close()
SockServer.Close
End Sub
Private Sub SockServer_ConnectionRequest(ByVal requestID As Long)
SockServer.Close
SockServer.Accept requestID ′表示客户请求连接的ID号
End Sub
′当客户向服务器发送数据到达后,产生DataArrival事件,在事件中接收数据,GetData方法接收数据。
Private Sub SockServer_Data
Arrival(ByVal bytesTotal As Long)
Dim s As String
SockServer.GetData s
Text1.Text = s
End Sub
当需要向客户发送数据时，只需调用SendData方法。
Private Sub Command1_Click()
SockServer .SendData Text2.Text
End Sub
②创建客户
要创建客户连接服务器，首先设置服务器主机名，如IP地址、域名或计算机名，然后设置服务器端口，最后连接服务器。
建立一窗体，并向其增加一个Winsock控件(可在工程菜单中的部件项来添加此控件)，取名为：SockC1。添加两文本框Text1,Text2,和一按钮Command1
Private Sub Form_Load()
SockCl.RemoteHost =′127.0.0.1″
′表示服务器主机名
SockCl.RemotePort = 2000
′表示服务器端口名
SockCl.Connect
′连接到服务器
End Sub
Private Sub Form_Unload(Cancel As Integer)
SockCl.Close
End Sub
Private Sub SockCl_Close()
SockCl.Close
End Sub
Private Sub SockCl_DataArrival(ByVal bytesTotal As Long)
Dim s As String
SockCl.GetData s ′接收数据到文本框中
Text1.Text = s
End Sub
Private Sub Command1_Click()
SockCl.SendData Text2.Text ′向服务器发送数据
End Sub
③进行通信
把这两个窗体分别编译成两个EXE文件，服务器Server.exe和客户Client.exe程序，并把它们分别安装在服务器端和客户端，这样就可以实现两者通信了。
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B. java网络编程应该怎样在客户端和服务器间实现通信

以前写的，照贴了。。。服务器端：import java.awt.*;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.*;
import java.net.*;/*6、 采用UDP协议，编写一个Java网络应用程序，该应用分服务器端程序和客户端程序两部分。
* 客户端指定一个服务器上的文件名，让服务器发回该文件的内容，或者提示文件不存在。
* （20分）（服务端程序和客户端程序分别命名为Server.java和Client.java）*/
public class N4BT6 extends Frame
{
DatagramSocket socket ;
DatagramPacket packet ;byte[] buf ;
File file ;
FileInputStream input;
String message = "该文件不存在";
TextArea text;
public N4BT6(String title)
{
super(title);
text = new TextArea(6,4);
add(text);
setSize(400, 300);
setVisible(true);
addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
dispose();
}
});

buf = new byte[1024];
try
{
socket = new DatagramSocket(1230);
packet = new DatagramPacket(buf, buf.length);
socket.receive(packet);
file = new File(new String(packet.getData()));
socket = new DatagramSocket();
}
catch (Exception e)
{e.printStackTrace();
}

if(file.exists())
{
try
{
buf = new byte[(int)file.length()];
packet = new DatagramPacket(buf,buf.length,InetAddress.getLocalHost(),1234);
input = new FileInputStream(file);
input.read(buf);
socket.send(packet);
}
catch (IOException e)
{
e.printStackTrace();
}
}
else
{
try
{
packet = new DatagramPacket(message.getBytes(),message.getBytes().length,
InetAddress.getLocalHost(),1234);
socket.send(packet);
}
catch (Exception e)
{
e.printStackTrace();
}
}

}
public static void main(String[] args)
{
new N4BT6("Server");
}
}
客户端：import java.awt.*;
import java.awt.event.*;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;public class N4BT6_2 extends Frame
{
TextArea text;
String message = "Q.txt";
DatagramSocket socket ;
DatagramPacket packet;
byte[] buf;
public N4BT6_2(String title)
{
super(title);
text = new TextArea(6,4);
add(text);
setSize(400, 300);
setVisible(true);
addWindowListener(new WindowAdapter()
{
public void windowClosing(WindowEvent e)
{
dispose();
}
});
try
{

socket = new DatagramSocket();
packet = new DatagramPacket(message.getBytes(),message.getBytes().length,
InetAddress.getLocalHost(),1230);
socket.send(packet);
}
catch (Exception e)
{
e.printStackTrace();
}

try
{
buf = new byte[1024];
socket = new DatagramSocket(1234);
packet = new DatagramPacket(buf,buf.length);
socket.receive(packet);
text.append(new String(buf));
}
catch (Exception e)
{
e.printStackTrace();
}
}
public static void main(String[] args)
{
new N4BT6_2("Client");
}
}

C. 用C语言编写服务器端和客户机端的关键部分代码！

//服务端 C++
#include "stdafx.h"
#include "stdio.h"
#include "winsock2.h"
#include <vector>
using std::vector;

SOCKET s;
vector<SOCKET> cc;

void onAccept()
{
sockaddr_in sa;
int add_len = sizeof(sa);
SOCKET c = accept(s,(sockaddr*)&sa,&add_len);
if(c!=INVALID_SOCKET)
{
printf("client:%s port:%d connected!\n",inet_ntoa(sa.sin_addr),sa.sin_port);
send(c,"hello",5,0);
cc.push_back(c);
}
else
{
printf("invalid connect\n");
}
}

void onRecv(const fd_set &fs)
{
for(int i=0;i<cc.size();++i)
{
if(FD_ISSET(cc[i],&fs))
{
char buffer[256]={0};
int rc= recv(cc[i],buffer,255,0);
if(rc>0)
{
printf("recv msg:%s\n",buffer);
send(cc[i],buffer,strlen(buffer)+1,0);
}
else if(rc == SOCKET_ERROR)
{
printf("recv msg failed:%d\n",::WSAGetLastError());
closesocket(cc[i]);
cc.erase(cc.begin()+i);
break;
}
}
}
}

int main(int argc, char* argv[])
{
//init
WORD wVersionRequested;
WSADATA wsaData;
wVersionRequested = MAKEWORD( 2, 2 );
WSAStartup( wVersionRequested, &wsaData );

s = socket(AF_INET,SOCK_STREAM,0);
if(s!=INVALID_SOCKET)
{
printf("create socket success!\n");
}

{
sockaddr_in sa;
sa.sin_family = AF_INET;
sa.sin_port = htons( 1500 );
sa.sin_addr.s_addr = 0 ; //*²»Ö¸¶¨µØÖ·
int rc = bind(s,(sockaddr *)&sa,sizeof(sa));
if(rc == SOCKET_ERROR)
{
printf("bind failed:%d\n",::WSAGetLastError());
return -1;
}
}

listen(s,SOMAXCONN);

timeval timeout={0,100};

while(true)
{
fd_set fs;
FD_ZERO(&fs);
FD_SET(s,&fs);

int rc = select(0,&fs,0,0,&timeout);
if(rc>0)
{
onAccept();
}
else if(rc == 0)
{
//printf("no connect!\n");
}
else
{
printf("select1 error:%d\n",::WSAGetLastError());
}

if(cc.size()>0)
{
FD_ZERO(&fs);
for(int i=0;i<cc.size();++i)
{
FD_SET(cc[i],&fs);
}

rc = select(0,&fs,0,0,&timeout);
if(rc>0)
{
onRecv(fs);
}
else if(rc == 0)
{
//printf("no recv!\n");
}
else
{
printf("select2 error:%d\n",::WSAGetLastError());
}
}
}

closesocket(s);

//clean
WSACleanup( );
return 1;
}

//=====================[client]====================
#include "stdafx.h"
#include <stdio.h>
#include <winsock2.h>
#include <windows.h>
#include <process.h>

SOCKET c;

unsigned int __stdcall myrecv(void *)
{
while(true)
{
char recv_buffer[256]={0};
int rc =recv(c,recv_buffer,255,0)>0;
if(rc>0)
{
printf("recv:%s\n",recv_buffer);
}
else if(rc==SOCKET_ERROR)
{
printf("recv failed:%d\n",::WSAGetLastError());
break;
}
}
_endthreadex(0);
return 0;
}

int main(int argc, char* argv[])
{
//init
WORD wVersionRequested;
WSADATA wsaData;
wVersionRequested = MAKEWORD( 2, 2 );
WSAStartup( wVersionRequested, &wsaData );

c = socket(AF_INET,SOCK_STREAM,0);
if(c!=INVALID_SOCKET)
{
printf("create socket success!\n");
}

//connect
{
sockaddr_in sa;
sa.sin_family = AF_INET;
sa.sin_port = htons( 1500 );
sa.sin_addr.s_addr = inet_addr("127.0.0.1") ; //*²»Ö¸¶¨µØÖ·
int rc = connect(c,(sockaddr *)&sa,sizeof(sa));
if(rc == SOCKET_ERROR)
{
printf("connect failed:%d\n",::WSAGetLastError());
return -1;
}
}

_beginthreadex(0,0,&myrecv,0,0,0);

int count = 0;
timeval timeout={0,100};
while(true)
{
char send_buffer[256]={0};
sprintf(send_buffer,"s%d",count++);
int rc = send(c,send_buffer,strlen(send_buffer),0);
if(rc>0)
{
printf("send:%s\n",send_buffer);
}
else if(rc==SOCKET_ERROR)
{
printf("send failed:%d\n",::WSAGetLastError());
break;
}
}

closesocket(c);
//clean
WSACleanup( );
return 0;
}