java - 简单 Java Web 代理 SocketException : Socket is closed

Question

上下文

我正在尝试使用 Java 构建一个简单的 HTTP Web 代理。现在我所拥有的就是在端口 5041 上监听 HTTP 请求的东西。现在我有2节课。 Proxy 类在端口上打开一个 ServerSocket，我将此套接字称为 welcomeSocket。打开此端口后，每次 welcomeSocket 接受新套接字时，Proxy 都会启动一个新的 Connection 线程。 Connection 类有一些简单的逻辑来读取 HTTP 请求 header 信息。稍后将扩展该类以获得更多功能。感谢您的帮助。

问题

当我运行代理并将浏览器配置为指向代理时，我收到 SocketException 错误，表明我的套接字已关闭。我不确定这些是怎么发生的。此外，Connection 线程似乎正在创建，但不一定输出 HTTP header 信息。这是显而易见的，因为输出显示重复的 NEW connection thread created 打印，但打印后没有标题信息。

代理类

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class Proxy {
    // Port is 5000 + 41
    private final int PORT;
    private ServerSocket welcomeSocket = null;
    private boolean listening = true;

    public Proxy(int port) {
        PORT = port; 

        try {
            welcomeSocket = new ServerSocket(PORT);
            listenForConnectionRequests();
        } catch (IOException e) {
            System.err.println("There was a problem while creating the welcome socket");
            e.printStackTrace();
            System.exit(-1);
        }
    }

    public void listenForConnectionRequests() {
        System.out.println("Listening for connection requests at " + PORT + "\n");

        while (listening) {
            try {
                new Connection(welcomeSocket.accept()).start();
            } catch (IOException e) {
                System.err.println("I/O error occured while waiting for a connection.");
                e.printStackTrace();
            }
        }
    }
}

连接类

public class Connection extends Thread {
    private Socket connectionSocket = null;
    private ArrayList<String> requestHeaders = new ArrayList<String>();
    private boolean running = true;
    private OutputStream os;
    private InputStream is;

    public Connection(Socket connectionSocket) {
        super("Proxy");
        System.out.println("NEW connection thread created");
        this.connectionSocket = connectionSocket;
    }

    public void run() {
        while (running) {
            readHttpHeader();
        }
    }

    private void stopRunning() {
        running = false;
        System.err.println("Stopping thread.");
        closeEverything();
    }

    private void readHttpHeader() {
        try {
            os = connectionSocket.getOutputStream();
        } catch (IOException e) {
            System.err.println("Problem getting output stream from connection socket.");
            e.printStackTrace();
            stopRunning();
        }

        try {
            is = connectionSocket.getInputStream();
        } catch (IOException e) {
            System.err.println("Problem getting input stream from connection socket.");
            e.printStackTrace();
            stopRunning();
        }

        String input;
        BufferedReader in = null;
        DataOutputStream out = null;
        try {
            in = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));
            out = new DataOutputStream(connectionSocket.getOutputStream());

            while ((input = in.readLine()) != null) {
                requestHeaders.add(input);
                System.out.println(input);
            }

        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } finally {
            try {
                if (in != null)
                    in.close();
                if (out != null)
                    out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

    private void closeEverything() {
        try {
            connectionSocket.close();
            is.close();
            os.close();
        } catch (IOException e) {
            System.err.println("Problem closing connection or streams");
            e.printStackTrace();
            stopRunning();
        }
    }
}

测试一些网页后的输出

Listening for connection requests at 5041

NEW connection thread created
GET http://127.0.0.1:63342/browserConnection/buildInfo HTTP/1.1
Host: 127.0.0.1:63342
Proxy-Connection: keep-alive
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.116 Safari/537.36
Accept: */*
DNT: 1
Accept-Encoding: gzip, deflate, sdch
Accept-Language: en-US,en;q=0.8

NEW connection thread created
NEW connection thread created
GET http://google.com/ HTTP/1.1
Host: google.com
Proxy-Connection: keep-alive
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.116 Safari/537.36
X-Client-Data: CKK2yQEIwbbJAQj9lcoB
DNT: 1
Accept-Encoding: gzip, deflate, sdch
Accept-Language: en-US,en;q=0.8
Cookie: OGP=-5061574:; SID=DQAAAMoCAACmU0EuiAZrQAuo8mgssp5cukiLvNn13ryGL2GeGswaF8Cmv2NIxyW_nnC7ihLpQRaY0gdlYg4K91TStT2aPHo3PWFhExCr5zD0yywqgMwsXuWgQedtdi8Lc6tsL0Nz2WSt8j1Is6Dw53SYpWw-Ukis9d386YATJRYdsDUhVsb3h-pe-QrKNBL3deaxIlMIb5itaAWVTSVkRUVcocns6S-mAopRFT-k8YMKXKVeouztBQhblI1YQUKAtMCqv55ZllmFyfZSQcqmbcsJx19ofBLnl6u2KByIwBLwMMa1DrK1YketAgvgxUzlrfanvTm94VQ7Lie9rppG-up1cNlDsu4XbXrIOkG2bdbD7J2SdjwmI_Hf9IrLl3IelDvdCfQol3CT8rdAMk1p7zBMQq5L_JfiiCLmjNd9VA0CiadcB-6dIBWnGGThNYEOkrU11i2qeiEPtvJqDx_7kyuphkFuQh8b5GI7f5xg-uVmLfjaO4Q7q5EiV7BTt5jacajRibvPsqK77lEw9_UTnPvXOkW1jmfJOKx85rAztVpV2vymO_dGMiG_ehiD4R6CO6ifCnHjij5TKUeWeSEzQdtdDsKGL3MAMSg1bZVKcmc3Veq77AwWZa996gUkyEdD1dJ5c4eTodTEjTx8KiUDEufPGxQtjyOEuT8rnY_MWvDTFUx0os-aMZfcYsLrTmJ6mWpYzKa5wnCvFHKnjBL24UddbBmhhaklLcOghJEH8kcVEVWvNuKC145OIzxwZA2CmTCfEDzymOd6pTGlwl9P7VInl2ro_SkoNmEn6VqUWLRC0zH1jEWZhpkNf9kbpLmWBS-xLWMBpvgPu7ysVBf7qR8_YlzyVprCdRDAR4mrciRaOaswHvWCWgU8EJk_gF8PgiP_D2WEtw8uJR6b4IL_ggxpmckGdHM7yUvkel9jWeFQxrazmF1f1c6SHBooSO6t-tCW7-Hw44A; HSID=A_KCc1Le4o6JlU760; APISID=hE0OzriLy98RcM4M/ALgi7Gky2rmmyyiDE; NID=77=dmymZT8yk5KfHAaIyzxhzvKfG_fvBjPwDpg-yTfz_5cBDKAsqL9n010br6xg1dSRrSKhS--_RYLoCuDodOzAHiaWS11pBB-4Npc9eQbqwkLnaf-nzeqNC_fwNSDElB7qfUmmvnZSHX1mowllXfpIM8cLm-ewYD0tGdHbpfvbAxkfH_jIwQKj-pS0f6ZkcodJ2CEEeoDhMUbZDAOfBKUUhM5qvLxE3curLhef6pftojQo0QpTumhoky2_pWR1lWP-5W0lPN29lMDSdeYrW5Umz_3jNHPRyMiGFwzNMIV9r9RUoyO50JreK057mDnzNygESvk_fBHlt49b2U6tesQ5NAtaAmL4VaWsAuj3jKEvjWTxSgSVrUeWwPC84hjn3liuGlBulWg; OGPC=5061900-22:5061918-27:5061934-15:5061921-40:5061937-46:5061933-25:5061941-6:5061574-1:5061940-57:5061952-26:5061975-14:5061983-7:

Problem getting output stream from connection socket.
java.net.SocketException: Socket is closed
    at java.net.Socket.getOutputStream(Socket.java:916)
    at Connection.readHttpHeader(Connection.java:46)
    at Connection.run(Connection.java:34)
Stopping thread.
Problem getting input stream from connection socket.
java.net.SocketException: Socket is closed
    at java.net.Socket.getInputStream(Socket.java:876)
    at Connection.readHttpHeader(Connection.java:54)
    at Connection.run(Connection.java:34)
Stopping thread.
java.net.SocketException: Socket is closed
    at java.net.Socket.getInputStream(Socket.java:876)
    at Connection.readHttpHeader(Connection.java:65)
    at Connection.run(Connection.java:34)
Problem getting output stream from connection socket.
java.net.SocketException: Socket is closed
    at java.net.Socket.getOutputStream(Socket.java:916)
    at Connection.readHttpHeader(Connection.java:46)
    at Connection.run(Connection.java:34)
Stopping thread.
Problem getting input stream from connection socket.
java.net.SocketException: Socket is closed
    at java.net.Socket.getInputStream(Socket.java:876)
    at Connection.readHttpHeader(Connection.java:54)
    at Connection.run(Connection.java:34)
Stopping thread.
java.net.SocketException: Socket is closed
    at java.net.Socket.getInputStream(Socket.java:876)
    at Connection.readHttpHeader(Connection.java:65)
    at Connection.run(Connection.java:34)
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
NEW connection thread created
GET http://www.yelp.com/ HTTP/1.1
Host: www.yelp.com
Proxy-Connection: keep-alive
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/48.0.2564.116 Safari/537.36
DNT: 1
Accept-Encoding: gzip, deflate, sdch
Accept-Language: en-US,en;q=0.8
Cookie: __cfduid=dd3ccfb39916d84ca8053ba95c0ca89fe1457229239; yuv=pOdmTZnrxWdr1NhFcLyF8cCB7Pj5l2tN3CSqNp0fiz0yKun0fbD0MHFrIo4K432S0pKC_-Sl9QijvKAX5u1iUJMmwZ2EnL4p; hl=en_US; fd=0; D_SID=172.250.60.189:SscPaGXtn/I/Skx3ISxQZOtF5qtsm+TmywEwnqXsiuo; qntcst=D%2CT%2C43606%2C43604%2C43602%2C43597%2C43596%2C43595%2C43583%2C43582%2C43581%2C37336%2C34588%2C34585%2C27425%2C27424%2C20052%2C20047%2C20040%2C20021%2C20020%2C20015%2C19991%2C19989%2C19958%2C19948%2C19947%2C19945%2C19944%2C19942%2C19941%2C19939%2C19936%2C19934%2C19932; __qca=P0-1476739725-1457229248633; fbm_97534753161=base_domain=.yelp.com; location=%7B%22city%22%3A+%22Seattle%22%2C+%22zip%22%3A+%22%22%2C+%22country%22%3A+%22US%22%2C+%22address2%22%3A+%22%22%2C+%22address3%22%3A+%22%22%2C+%22state%22%3A+%22WA%22%2C+%22address1%22%3A+%22%22%2C+%22unformatted%22%3A+%22seattle%22%7D; bse=b955bbc7020253479a51b278e343d766; __utma=165223479.439363298.1457229244.1457383227.1457394139.4; __utmc=165223479; __utmz=165223479.1457383227.3.3.utmcsr=google|utmccn=(organic)|utmcmd=organic|utmctr=(not%20provided); __utmv=165223479.|4=account%20level=anon=1; _ga=GA1.2.C1BEB9B4D17FEEDD; D_PID=469F0452-18FF-3E05-8072-566D9785BE96; D_IID=EC337894-ADD2-36A6-848D-AA87DA4B1407; D_UID=6E67A9C8-F999-33A6-8838-4EBFBC9B943E; D_HID=qXtXeOzvXZDnGT33GPaUewyWk7KgXdgunNy1mqdkX7g

Problem getting output stream from connection socket.
Problem getting output stream from connection socket.
Problem getting output stream from connection socket.
Problem getting output stream from connection socket.

Answer 1

您正在关闭套接字，然后尝试从中读取数据。

下面的代码将调用readHttpHeader两次...

while (running) {
    readHttpHeader();
}

第一次成功:

try {
    in = new BufferedReader(new InputStreamReader(connectionSocket.getInputStream()));

    while ((input = in.readLine()) != null) {
        requestHeaders.add(input);
        System.out.println(input);
    }

然后关闭输入流...

} finally {
    try {
        if (in != null)
            in.close();

关闭它所包装的流(InputStreamReader)，进而关闭套接字的输入流。

然后循环第二次调用 readHttpHeader()，这会发现流已关闭。几个 try-catch block 捕获一些错误，将它们报告给 stderr，然后继续前进，到达读取循环(失败)，最后关闭流。最后，由于 running 为 false，因此不会第三次调用 readHttpHeader()。