HTTP代理服务器Java错误

Question

• As an assignment, I am allowed to use ServerSocket and Socket class only. Also it should be single-threaded as well.

I'm implementing a HTTP proxy server in Java, first it fetches request from client and then pushes to server, and then pushes the response back to the client.

The problem

The problem is, I have successfully get the request, send it to the end-server and get the proper HTTP response. I also can do print out the response in console . But it got stuck when I send the response to clientServer.outputstream. Firefox (requested to use, HTTP 1.0, no keep-alive requested) seems to load forever and nothing shows, and no response Firefox received from my program as well.

What I inspect when debug

Everytime a page start to load (FF request), there are always 2 client sockets. First socket contains null request , and second socket contains proper request . What I expect was that only one proper HTTP request from Firefox. Is that a weird behavior?

example:

/0:0:0:0:0:0:0:1:65194
[null request]

/0:0:0:0:0:0:0:1:65195
GET http://www.microsoft.com/ HTTP/1.0
Host: www.microsoft.com
User-Agent: Mozilla/5.0 (Windows NT 6.2; WOW64; rv:15.0) Gecko/20100101 Firefox/15.0.1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-us,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: close
Proxy-Connection: close
Cookie: viewkey=lightweight; WT_FPC=id=269eb0e7618962f93a81347585923074:lv=1349229942007:ss=1349229580158; WT_NVR_RU=0=technet|msdn:1=:2=; omniID=c736269c_f430_4e9b_a42a_23a0c965c60a; MUID=212A1766CFE761423CD014BDCBE76158&TUID=1; MC1=GUID=08600fba7f5c5f409e67980d8a027593&HASH=ba0f&LV=20129&V=4&LU=1347643534618; A=I&I=AxUFAAAAAADGBwAA8ezRtqBBHjk3++mP1Bwj9w!!&V=4&CS=119EQ5002j10100; msdn=L=en-US

Code

ServerSocket serverSocket;
try {
    serverSocket = new ServerSocket(60000);
    while (true) {
            clientSocket = serverSocket.accept();
            [...]
            // Extract request, and push to end-server
            // Fetch response from end-server to client, using flush() already
            // Close all input, output
            // Close all sockets
} catch {[...]}

Any help is welcomed, thank you!

Full code as requested, I use PrintWriter, but before that using Byte makes no difference (not care efficiency)

import java.io.*;
import java.net.*;
import java.util.*;

public class Proxy {

    static String separator = System.getProperty("line.separator");

    public static void main(String args[]) {
        //int port = Integer.parseInt(args[0]); 
        start(60000);
    }

    public static void start(int port) {
        ServerSocket serverSocket;
        try {
            serverSocket = new ServerSocket(port);
            Socket clientSocket = null;
            while (true) {
                clientSocket = serverSocket.accept();

                System.out.println(clientSocket.getRemoteSocketAddress() + "\n" + clientSocket.getLocalSocketAddress() + "\n" + clientSocket.getInetAddress());

                BufferedReader inStreamFromClient = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));

                String inLine;
                Vector<String> clientRequestHeader = new Vector<String>();
                String rawRequest = "";

                while ((inLine = inStreamFromClient.readLine()) != null) {
                    if (!inLine.isEmpty()) {
                        clientRequestHeader.add(inLine);
                        rawRequest = rawRequest.concat(inLine + separator);
                    } else break;
                }

                while ((inLine = inStreamFromClient.readLine()) != null) 
                    rawRequest = rawRequest.concat(inLine + separator);

                System.out.println(rawRequest);

                if (!rawRequest.isEmpty()) {
                    handleRequest(clientSocket, clientRequestHeader, rawRequest);
                } else {
                    //clientSocket.close();
                                    // Not sure how to handle null request
                }

            }
        } catch (Exception e) {e.printStackTrace();}

    }

    public static void handleRequest(Socket clientSocket, Vector<String> clientRequestHeader, String rawRequest) {
        HTTPRequest request = new HTTPRequest(clientRequestHeader, rawRequest);
        try {
            //System.out.println(rawRequest);

            // Send request to end-server
            Socket endServerSocket = new Socket(request.getHost(), 80);

            PrintWriter outStreamToEndServer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(endServerSocket.getOutputStream())));
            BufferedReader stringReader = new BufferedReader(new StringReader(rawRequest));
            String inLine;
            while ((inLine = stringReader.readLine())!= null) {
                outStreamToEndServer.println(inLine);
            }
            outStreamToEndServer.println();
            outStreamToEndServer.flush();


            // Read response header from end-server
            String responseHeader = "";
            BufferedReader inStreamFromEndServer = new BufferedReader(new InputStreamReader(endServerSocket.getInputStream())); 
            while (!(inLine = inStreamFromEndServer.readLine()).isEmpty()) {
                responseHeader = responseHeader.concat(inLine + separator);
            }

            // Send response header to client
            PrintWriter outStreamToClient = new PrintWriter(new BufferedWriter(new OutputStreamWriter(clientSocket.getOutputStream())));
            outStreamToClient.println(responseHeader);
            outStreamToClient.flush();

            // Send response body to client
            String responseBody = "";
            while ((inLine = inStreamFromEndServer.readLine()) != null) {
                responseBody = responseBody.concat(inLine + separator);
            }
            outStreamToClient.println(responseBody);
            outStreamToClient.flush();

            endServerSocket.shutdownInput();
            clientSocket.shutdownOutput();
            clientSocket.close();
            endServerSocket.close();

            //endServerSocket = null;
        } catch (Exception e) {
            e.printStackTrace();
        } 
    }

}

Answer 1

first you should not use PrintWriter to transfer the Data, because the HTTP protocol isn't a pure text protocol the body can contain some raw data like images.

Replace your response transfer code with the code below.

InputStream in = endServerSocket.getInputStream();
OutputStream out = clientSocket.getOutputStream();
byte[] buffer = new byte[1024];
int bytesRead;
while ((bytesRead = in.read(buffer)) != -1)
{
    out.write(buffer, 0, bytesRead);
}

in.close();
out.close();

Second point, you add always as line break the

 static String separator = System.getProperty("line.separator");

This is the System specific line seperator. HTTP defines for the HTTP header and for the http header and body separation the ctrl line break charaters, so change this.

 static String separator = "\r\n";

With this changes you will get your response to your browser.

Last Point you should change your client request read code also, because it will not always work if you want POST some data. Sometimes this data will transfered as raw data, by example file uploads.

Good Luck