Unable to correct StreamCorruptedException in full duplex code

Question

I am trying to implement a full duplex TCP connection between two applications.

My gist of the idea is to do the following :

Client

socket.connect(ServerAddress,Timeout);
socketArray.add(socket);
outputStream = new ObjectOutputStream(socket.getOutputStream());
outputStream.writeObject(message);
outputStream.flush();

/** Wait for reply**/
inputStream = new ObjectInputStream(socket.getInputStream());
message     = (Message)inputStream.readObject();

if (message.type == X) {
   replyToServer(message,socketArray);
}  

replyToServer(Message,socketArray) {
  for(Socket socket : socketArray) {
      outputStream = new ObjectOutputStream(socket.getOutputStream());  // **getting streamCorruptedException** here
      outputStream.writeObject(message);
      outputStream.flush();

  }

}

Server

Here I listen to the incoming connections, and dependent on the message type, I want to reply to it after changing some parameters of the message.

inputStream = new ObjectInputStream(clientSocket.getInputStream()); //notice inputStream and outputStream are created only once here, maybe that is the issue ?
outputStream = new ObjectOutputStream(clientSocket.getOutputStream());
while ( (message = (Message)inputStream.readObject() ) != null) {
  if (message.type == Y) {
     message.type = X ; //notice this is used in Client code
     outputStream.writeObject(message);
     outputStream.flush();           
  } else if (message.type == X ) {
    // don't send anything to client, we are done processing this message
  }
}

After looking around in google, I got some idea that ObjectInputStream and ObjectOutputStream must be somehow synchronized. But I did not get a concrete understanding. If someone can point out mistake in my code, it will be helpful.

Code flow :

Client sends a message to server with message type Y, asking for information.
Server sees the type Y, sets information in the object, changes message type to X, and replies to client.
Client receives replies from all others. Note : There are 5 applications running both server and client. Hence the client will wait until it gets replies from all the others before proceeding.

Now client must send the received information to all 5 applications, and does that in replyToServer method. The exception occurs there.

PS : This is pseudo code, and if any more details are required to understand code flow , please let me know in the comments.

Actual stack trace

err: java.io.StreamCorruptedException
err: at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1530)
err:     at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:1483)

.....`

user207421 · Answer 1 · 2017-08-25T00:34:39.367

outputStream = new ObjectOutputStream(socket.getOutputStream());  // **getting streamCorruptedException** here

Impossible. You are getting StreamCorruptedException: invalid type code AC at the other end when you execute new ObjectInputStream(...).

The reason is that you've created multiple ObjectOutputStreams for the same socket, but without creating correspondingly multiple ObjectInputStreams at the peer. You should use the same object input and output streams for the life of the socket, at both ends.

while ( (message = (Message)inputStream.readObject() ) != null) {

This isn't valid either. ObjectInputStream.readObject() doesn't return null at end of stream. It can return null any time you wrote a null. The loop should terminate when EOFException is thrown.

Unable to correct StreamCorruptedException in full duplex code

1 Answers1