Question

I’m trying to send a public key object of type Key to my Server. But I didn’t get this running. The prototocl looks the following:

[Command]\n[serialized Key object]

The client uses this code:

Socket admin;
PrintWriter pw;
OutputStream os;
BufferedReader is; 
for(int tries = 0; tries < MAX_RECONNECT_TRIES_ADMIN_SERVER; tries++)
{
    try 
    {
        admin = new Socket(host,port);
        os = admin.getOutputStream();
        is = new BufferedReader(new InputStreamReader(admin.getInputStream()));
        pw = new PrintWriter(new OutputStreamWriter(os));   

        AdminServerCommand.NODE_REGISTER.writeToPrintWriter(pw);
        pw.flush();

        sendPublicKey(os);

        String resultLine = null;
        resultLine = is.readLine();
        if(AdminServer.Feedback.KEY_REGISTERED.commandMatch(resultLine))
        {
            is.close();
            os.close();
            admin.close();
            return true;
        }
        is.close();
        os.close();
        admin.close();
        registerNodeRetrySleep(1000);
    }
    catch (Exception e) 
    {}
}
return false;

public void sendPublicKey(OutputStream out)
{
    try
    {
        ObjectOutputStream outO = new ObjectOutputStream(out);
        outO.writeObject(cyper.getPublicKey());
        outO.flush();
    }
    catch (Exception ex)
    {
        ex.printStackTrace();
    }
}

public void writeToPrintWriter(PrintWriter os)
{
    if(os == null)
        throw new IllegalArgumentException("Can not write command to null stream.");
    os.println(comm);
    os.flush();
}

The Server uses

String com = "";
    try 
    {
        if(client.getInputStream().available() > 2)
        com = is.readLine();
    }
    catch (IOException e) 
    {
        errorResponse(Error.COMMAND_ERROR);
    }
    Key key = null;
    try
    {
        ObjectInputStream keyIn = new ObjectInputStream(client.getInputStream());
        key = (Key)keyIn.readObject();
    }
    catch(Exception b)
    {
        b.printStackTrace();
        errorResponse(Error.BAD_KEY);
        return;
    }

The Exception looks the following:

Nov 28, 2012 9:52:59 PM AdminServer.AdminServer run
INFO: Get a new request
java.io.StreamCorruptedException: invalid stream header: 73720014
    at java.io.ObjectInputStream.readStreamHeader(Unknown Source)
    at java.io.ObjectInputStream.<init>(Unknown Source)
    at AdminServer.AdminServer.registerNewKeyEntry(AdminServer.java:115)
    at AdminServer.AdminServer.run(AdminServer.java:65)
    at java.lang.Thread.run(Unknown Source)
Nov 28, 2012 9:52:59 PM AdminServer.AdminServer errorResponse
WARNING: Error: Bad public key format. Use object stream with key object.

Does anybody now how I can solve this. The type Key is an Interface type that implements itself the Interface Serializable. So it shouldn’t be a problem to serialize this object. I spend the whole evening with this Problem. Hope that anybody can help me getting rid of this.

Answer 1

There is not enough code in your question to diagnose completely – but here are a couple of observations.

This code looks suspicious:

if(client.getInputStream().available() > 2)
com = is.readLine();

Presumably you have a buffered reader is wrapping the client input stream. What happens if the if statement is not true – you skip reading the line? Now that line of text is still in the pipeline and will pass to your keyIn.readObject method. That could cause the corrupt error.

I would recommend just removing the whole if line. readLine() blocks anyways so there is no need for the check.

Also, are you absolutely sure that AdminServerCommand.NODE_REGISTER.writeToPrintWriter(pw); sends exactly one line of text with absolutely no characters after the line feed?

However – I think you have a bigger issue here. This design where you are switching back and forth between Java object serialization and manual text reading/writing is just a disaster waiting to happen. If you want to use object serialization, use it exclusively. You can alternate sending a String object, then a Key object and your stream won’t get corrupted because you sent one too many or one two few line breaks.

For example:
ObjectOutputStream outO = new ObjectOutputStream(out);

    String command = "whatever";
    outO.writeObject(command);
    outO.writeObject(cyper.getPublicKey());
    outO.flush();

Then on the server side, always use readObject, knowing that the first will be a command, the second will be a key.