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javasocketsstreamserversocket

Open more than one stream between socket and serversocket

I'm creating a simple chat in Java, and it works. I just have a problem when a client close the connection, because it continue to appear online. This is because there's no a way to know when a stream is closed.

I searched on google and any solution has not resolved my problem, so I want to send a boolean each 300ms and, if I don't receive any answer or I get an error, I can close the connection server side.

The problem is that there's a conflict in the stream, I can't know if I'm reading a boolean or a text, so sometimes my CheckConnection class try to read a string and my SocketHandler class try to read a boolean, and I receive an error. I use the class ObjectInputStream and ObjectOutputStream to read and write into the stream.

It's my first server application and I don't know very much about it, I don't know if it's possible open more than one stream or if there are other solutions, so I'm asking you. What may I do?

PS: I tried to create a PrintStream and execute the checkError() method, but it returns always false, even if I close explicitly all the streams client side. Thank you.

Solution

  • I suggest you use text as this is simpler to work with to start with.

    • treat any message as a heartbeat. If you get data, the connection is still good.
    • treat a heartbeat as a string and chat as a string. it's all a String so you don't need to worry about what it is.
    • check a stream is open by attempting to read from it and expecting you will get something within a timeout period.

    You can use BufferedReader, or Scanner to reads the text. You can user BufferedWriter to write the text.

    In your string you can create a simpler protocol like this.

    say [to-whom] [message ...]

    for the heartbeat you can have

    hb

    or

    heartbeat

    or

    say nobody hi

    You might add commands like

    login [user] [password]

    and

    kthxbye

    To decode the message, look at the first word and you know it's purpose and then read the second word for say and the rest of the string is the message.

    To test the protocol, you can telnet to the port and type in stuff to the server directly. You don't even need to write a client to start with.