java - SocketException - 'Socket is closed' 即使 isConnected() 返回 true

Question

我正在制作一个 android 应用程序，它使用套接字通信将图像发送到计算机上运行的 java 应用程序

发生的情况如下:桌面正在运行服务器 java 应用程序，客户端 Android 应用程序在设备上运行，它将图像传输到服务器，这部分运行顺利。之后，服务器应用程序从控制台获取一行并将其传递回 Android 应用程序。在 Android 应用程序收到该消息之前，它应该显示一个进度对话框，但它会卡在那里。 Android 应用程序应该使用 readLine() 读取桌面应用程序传递的字符串，但是当我尝试通过 Android 应用程序中的套接字打开输入流时，它给了我异常。

以下是代码，首先是桌面服务器，然后是 Android 客户端

导入java.net.ServerSocket;导入java.net.Socket；导入java.io.*;

class ProjectServer
{
    ServerSocket serSock;
    Socket  sock;

    BufferedReader in;
    PrintWriter out;
    public static void main(String ar[])
    {
        try
        {
            ProjectServer cs=new ProjectServer();
            cs.startServer();
        }
        catch(Exception e)
        {

        }
    }

    public void startServer()
    {
        try
        {
            serSock=new ServerSocket(8070);
            System.out.println("Waiting for client...");
            sock=serSock.accept();


            System.out.println("Connections done");


            //Accept File
            System.out.println("Connected");
            System.out.println(sock.isConnected()+"1");

            //receive code

            int filesize=450660;
            int bytesRead;
            int current=0;
            // receive file
            byte [] mybytearray  = new byte [filesize];
            InputStream is = sock.getInputStream();
            FileOutputStream fos = new FileOutputStream("C:\\Project Server\\Capture.png");
            BufferedOutputStream bos = new BufferedOutputStream(fos);
            bytesRead = is.read(mybytearray,0,mybytearray.length);
            current = bytesRead;


            do {
               bytesRead =
                  is.read(mybytearray, current, (mybytearray.length-current));
               if(bytesRead >= 0) current += bytesRead;
            } while(bytesRead > -1);

            bos.write(mybytearray, 0 , current);
            bos.flush();
            System.out.println("end-start");
            bos.close();
            //sock.close();
            //receive code ends

            //System.out.println(br.readLine());


            //Matlab computation

            //Send result
            System.out.println(sock.isConnected()+"2");
            PrintWriter pr=new PrintWriter(sock.getOutputStream(),true);

            pr.println((new BufferedReader(new InputStreamReader(System.in))).readLine());
            System.out.println(sock.isConnected()+"3");
            (new BufferedReader(new InputStreamReader(System.in))).readLine();
            System.out.println(sock.isConnected()+"4");
        }
        catch(Exception e)
        {
            System.out.println(e);
            e.printStackTrace();
        }

    }
}

Android 客户端:

package com.site.custom;

import java.io.BufferedInputStream;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.InputStreamReader;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.net.Socket;

import android.app.Activity;
import android.app.ProgressDialog;
import android.os.Bundle;
import android.util.Log;
import android.widget.TextView;


public class Act2 extends Activity
{
    private ProgressDialog pd;
    private String serverIP="58.146.100.187";
    private BufferedReader in;
    private PrintWriter out;
    private String path;
    private Socket cliSock;

    public void onCreate(Bundle onCreateInstance)
    {
        super.onCreate(onCreateInstance);
        setContentView(R.layout.act2);
        this.setTitle("This has started");
        path=getIntent().getStringExtra("path");

        //Establish Connection
        //pd=ProgressDialog.show(this, "Establishing connection", "Finding server",false,true);

        try
        {
            cliSock=new Socket(serverIP,8070);

            //pd.dismiss();
            //Log.v("MERA MSG","changing text");
            ((TextView)findViewById(R.id.tview)).setText(path);
        }
        catch(Exception e)
        {
            Log.v("MERA MSG",e.toString());
        }

        //Send file
        //Log.v("MERA MSG","changing text1");

        ProgressDialog pd=ProgressDialog.show(this, "Sending image", "Image chosen:"+path.substring(path.lastIndexOf("//")+1),false,true);
        //Log.v("MERA MSG","changing text2");

        try
        {


            File myFile = new File (path);
            System.out.println((int)myFile.length());
            byte[] mybytearray  = new byte[450560];
            FileInputStream fis = new FileInputStream(myFile);
            BufferedInputStream bis = new BufferedInputStream(fis);
            bis.read(mybytearray,0,mybytearray.length);
            OutputStream os = cliSock.getOutputStream();
            System.out.println("Sending...");
            os.write(mybytearray,0,mybytearray.length);
            os.flush();
            os.close();
            bis.close();
            //sock.close();
            //System.out.println("Completed");
            System.out.println(cliSock.isConnected()+"1");
            pd.dismiss();
            //System.out.println("Done");
            System.out.println(cliSock.isConnected()+"2");
            //Show dialog box till computation results arrive
            pd=ProgressDialog.show(this, "Recognizing...", "(waiting for server reply)",false,true);
            System.out.println(cliSock.isConnected()+"3");
            in=new BufferedReader(new InputStreamReader(cliSock.getInputStream()));
            System.out.println(in.readLine());
            pd.dismiss();

        }
        catch(Exception e)
        {
            Log.v("MERA MSG",e.toString());
            e.printStackTrace();
        }



    }
}

顺便说一句，这是来自 LogCat 的日志: http://pastebin.com/atHMycTa您可以确认套接字仍处于连接状态，因为它在第 350 行和第 349 行显示为 true查看第 351 行的错误。

Answer 1

isConnected() 只告诉您是否曾经连接过这个 Socket，因此它返回 true。它并不表示连接的状态。