使用DataInputStream和DataOutputStream和套接字的管道断开

Question

I set up a client and server sockets. When I use classes ObjectOutputStream and ObjectInputStream and the method readObject/writeObject everything works fine.

It simulates communication with a robot that I know for sure interprets correctly only method DataOutputStream.writeBytes.

So I set up the new architecture for simulation since the robot is not available for testing on a daily basis.

In the following code where ObjectOutputStream/ObjectInputStream readObject/writeObject were replaced with DataInputStream/DataOutputStream writeBytes and IOutils.toByteArray. The server socket correctly receives the message but when it tries to write back a response I get a broken pipe as if the connection was closed somewhere. Notice that I never close sockets or streams because the robot can answer even after 30 seconds. Any help to make DataOutputStream.writeBytes work would be appreciated.

Here's the non-working code:

Client:

Socket serverSocket =  new Socket("server", 9899);
DataOutputStream outputStream = new DataOutputStream(serverSocket.getOutputStream());
//ObjectOutputStream outputStream = new ObjectOutputStream(serverSocket.getOutputStream());
//outputStream.writeObject("\n" + "message" + "\r");
outputStream.writeBytes("\n" + "message" + "\r");
outputStream.flush();

DataInputStream inputStream = new DataInputStream(serverSocket.getInputStream());
//ObjectInputStream inputStream = new ObjectInputStream(serverSocket.getInputStream());
byte [] bytes = IOUtils.toByteArray(inputStream);
String serverResponse = new String(bytes,"UTF-8");
//  String serverResponse = (String)inputStream.readObject();

Server:

ServerSocket serverSocket = new ServerSocket(9899);

while (true) {

 Socket socket = serverSocket.accept();

//ObjectInputStream inputStream = new ObjectInputStream(socket.getInputStream());
DataInputStream inputStream = new DataInputStream(socket.getInputStream());
byte [] bytes = IOUtils.toByteArray(inputStream);
String message = new String(bytes,"UTF-8");
//String message = (String) inputStream.readObject();
Thread.sleep(15000);

//ObjectOutputStream outputStream = new ObjectOutputStream(socket.getOutputStream());
DataOutputStream outputStream = new DataOutputStream(socket.getOutputStream());
//outputStream.writeObject("server response");
outputStream.writeBytes("server response"); //EXCEPTION THROWN HERE FOR BROKEN PIPE
outputStream.flush();

            }

Thanks for your time

Answer 1

IOUtils.toString(InputStream) must read the stream until its end, which would imply that the peer has disconnected. So you can't write to it.

If you're exchanging Strings with data streams you should use writeUTF() and readUTF().

Or read and write lines, with a BufferedReader/Writer.