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POjava socket InputStream hangs/blocks on both client and server
 

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    <p><strong>Hi, all</strong></p> <p>I am recently working on a tiny program aimed to close the browser remotely. The basic procedures are as follow:<br> Server side:<br></p> <ol> <li>Create a SocketServer to listen to some certain port.</li> <li>Accept a connection and create a corresponding socket object</li> <li>Read the InputStream from the created socket(blocked on this operation) <br></li> </ol> <hr> <p>Client side:<br></p> <ol> <li>Create a socket object to establish a connection with the server.</li> <li>Send the command to close the browser on Server side by writing bytes to OutputStream.</li> <li>Read the feedback from the server by using read() on InputStream of the socket(blocked on this operation)</li> </ol> <hr> <p>Code Below:<br><br> <strong>Server.java</strong></p> <pre><code>package socket; import java.io.IOException; import java.net.InetAddress; import java.net.NetworkInterface; import java.net.ServerSocket; import java.net.Socket; import java.util.Enumeration; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class Server { private static ExecutorService es = Executors.newFixedThreadPool(5); public static void main(String[] args) throws IOException { InetAddress targetAddress = null; NetworkInterface ni = NetworkInterface.getByName("eth2"); System.out.println(ni); Enumeration&lt;InetAddress&gt; inetAddresses = ni.getInetAddresses(); while(inetAddresses.hasMoreElements()) { InetAddress inetAddress = inetAddresses.nextElement(); if(inetAddress.toString().startsWith("/10")) { targetAddress = inetAddress; break; } } ServerSocket sSocket = new ServerSocket(11111, 0, targetAddress); while(true) { System.out.println("Server is running..."); Socket client = sSocket.accept(); System.out.println("Client at: " + client.getRemoteSocketAddress()); es.execute(new ClientRequest(client)); } } } </code></pre> <p><br> <strong>ClientRequest.java</strong></p> <pre><code>package socket; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.Socket; public class ClientRequest implements Runnable { private Socket client; public ClientRequest(Socket client) { this.client = client; } @Override public void run() { try { System.out.println("Handled by: " + Thread.currentThread().getName()); // get input/output streams for client socket InputStream cis = client.getInputStream(); OutputStream cos = client.getOutputStream(); // buffer size : 1024 ? byte[] buffer = new byte[1024]; int recvSize; int totalRecvSize = 0; while(-1 != (recvSize = cis.read(buffer, totalRecvSize, 1024 - totalRecvSize))) { totalRecvSize += recvSize; } String command = new String(buffer, "utf-8"); System.out.println("Command from client: " + command); String commandNative = CommandMap.getNativeCommand(command.trim()); if(null != commandNative) { Process np = Runtime.getRuntime().exec(commandNative); InputStream is = np.getInputStream(); byte[] bufferProcess = new byte[1024]; int bytesRead; int totalBytesRead = 0; while(-1 != (bytesRead = is.read(bufferProcess, totalBytesRead, 1024 - totalBytesRead))) { totalBytesRead += bytesRead; } // give feed back of process output cos.write(bufferProcess); // close process input stream is.close(); } } catch (IOException e) { e.printStackTrace(); } finally { if(null != client) { try { client.close(); } catch (IOException e) { e.printStackTrace(); } } } } </code></pre> <p>and finally, <strong>Client.java</strong></p> <pre><code>package socket; import java.io.IOException; import java.io.InputStream; import java.io.OutputStream; import java.net.Socket; import java.net.UnknownHostException; import java.nio.charset.Charset; public class Client { private static final int BUF_SIZE = 1024; // feedback message size will not exceed 1024 bytes private static final byte[] BUFFER = new byte[BUF_SIZE]; public static void main(String[] args) throws UnknownHostException, IOException, InterruptedException { Socket socket = new Socket("10.117.37.176", 11111); System.out.println("Connected to Server..."); OutputStream os = socket.getOutputStream(); InputStream is = socket.getInputStream(); String command = "kill ie"; byte[] commandBytes = command.getBytes(Charset.forName("utf-8")); System.out.println("Send: " + command); os.write(commandBytes); System.out.println("After send: " + command); int totalRecv = 0; int recvSize; while(-1 != (recvSize = is.read(BUFFER, totalRecv, BUF_SIZE - totalRecv))) { totalRecv += recvSize; } String feedback = new String(BUFFER, "utf-8"); System.out.println("Feedback: " + feedback); socket.close(); } } </code></pre> <p>To reiterate the problems:<br></p> <ul> <li>The Server side can not read the command by calling read(buffer, offset, len) on InputStream object of the socket. It blocks.</li> <li>The Client side can not read the feedback by calling read(buffer, offset, len) on InputStream object of its socket. It blocks.</li> <li>But when I comment out the feedback reading operations in Client.java, both Server and Client work correctly.</li> </ul> <hr> <p>I am wondering what's the hidden causes in those codes ?<br> Hope someone can help me, thanks a lot !<br></p>
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