Question

我正在尝试编写一段代码来实现代理服务器。但是，我无法将数据发送回客户端，因为响应如下所示。

响应显示正常响应，稍后会出现一些响应，表示URI太大。

HTTP/1.1 414 Request-URI Too Large
Date: Sun, 01 Sep 2013 14:52:20 GMT
Server: Apache/2.2.22 (Ubuntu)
Vary: Accept-Encoding
Content-Length: 325
Connection: close
Content-Type: text/html; charset=iso-8859-1

<!DOCTYPE HTML PUBLIC "-//IETF//DTD HTML 2.0//EN">
<html><head>
<title>414 Request-URI Too Large</title>
</head><body>
<h1>Request-URI Too Large</h1>
<p>The requested URL's length exceeds the capacity
limit for this server.<br />
</p>
<hr>
<address>Apache/2.2.22 (Ubuntu) Server at 127.0.1.1 Port 80</address>
</body></html>

代码如下。

package ownproxy;

/**
 *
 * @author mklrjv
 */
import java.net.*;
import java.io.*;
import java.nio.CharBuffer;
import java.util.logging.Level;
import java.util.logging.Logger;

public class InterceptionProxy2 {

    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = null;
        boolean listening = true;
        int port = 1234;
        try {
            serverSocket = new ServerSocket(port);
        } catch (IOException e) {
            System.out.println("Port Error");
            System.exit(-1);
        }
        while (listening) {
            new ProxyThread2(serverSocket.accept()).start();
        }
        serverSocket.close();
    }
}

class ProxyThread2 extends Thread {

    private Socket socket = null;
    private static final int BUFFER_SIZE = 32768;

    public ProxyThread2(Socket socket) {
        super("ProxyThread2");
        this.socket = socket;
    }

    public void run() {
        PrintWriter outGoing = null;
        try {
            outGoing = new PrintWriter(socket.getOutputStream(), true);
            BufferedReader inComing = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            String incomingRequest;
            String url = "";
            String request = "";
            String response = "";
            //Take the incoming request
            char[] buf = new char[1000000];
            inComing.read(buf);
            request = new String(buf);
            //Create a new socket for connecting to destination server
            Socket connSocket = new Socket("localhost", 80);
            PrintWriter pOut = new PrintWriter(connSocket.getOutputStream(), true);
            BufferedReader pIn = new BufferedReader(new InputStreamReader(connSocket.getInputStream()));
            //Put data into the new socket(to the apache server) and receive its output
            pOut.print(request);
            pIn.read(buf);
            response = new String(buf);
            System.out.println(response);
            //Put data back into the original client socket
            outGoing.write(response);
        } catch (IOException ex) {
            Logger.getLogger(ProxyThread2.class.getName()).log(Level.SEVERE, null, ex);
        } finally {
            outGoing.close();
        }

    }
}

Answer 1

导致414错误的原因并不明显。如果您没有在代理上使用Web浏览器但是手动发送GET请求（或其他一些非http请求），则代码中的错误（见下文）可能会导致GET请求中包含超过8196个字符，这是Apache的默认限制。

您应该更改代码，以便使用String（缓冲区，偏移量，长度）构造函数创建字符串，该构造函数使用读取的字节数，而不是完整缓冲区，如果请求和可能包含许多NULL值。回应很短。此外，您应该考虑将输出刷新回代理客户端。这是您的代码与这些更改

public void run() {
  PrintWriter outGoing = null;
  try {
     outGoing = new PrintWriter(socket.getOutputStream(), true);
     BufferedReader inComing = new BufferedReader(new InputStreamReader(socket.getInputStream()));
     String incomingRequest;
     String url = "";
     String request = "";
     String response = "";
     //Take the incoming request
     char[] buf = new char[100000];
     int bytesRead = inComing.read(buf);
     request = new String(buf, 0, bytesRead);
     //Create a new socket for connecting to destination server
     Socket connSocket = new Socket("localhost", 10003);
     PrintWriter pOut = new PrintWriter(connSocket.getOutputStream(), true);

     //Reader for response from destination server
     BufferedReader pIn = new BufferedReader(new InputStreamReader(connSocket.getInputStream()));
     //Put data into the new socket(to the apache server) and receive its output
     pOut.print(request);
     pOut.flush();
     bytesRead = pIn.read(buf);

     if(bytesRead > 0) {
        response = new String(buf, 0, bytesRead);
     }

     System.out.println(response);
     //Put data back into the original client socket
     outGoing.write(response);
  } catch (IOException ex) {
     Logger.getLogger(ProxyThread2.class.getName()).log(Level.SEVERE, null, ex);
  } finally {
     outGoing.close();
  }

Answer 2

你不能写这样的HTTP代理。你需要两个线程，每个方向一个，都只复制字节。原因是HTTP保持活着。你无法分辨请求者在哪里结束响应就是解析头文件，块等等。这一切都变得太难了。

Java中的代理服务器：无法将响应发送回客户端

2 个答案: