CODEWITHSUNDEEP
javachatinputstreamoutputstreamprintwriter
Jonatan Stenbacka
Jonatan Stenbacka

Reputation: 1864

Creating an echo-server: Connected client gets IO-exception

I'm trying to create a single-threaded echo-server, but I can't figure out how to send the input from the client back to the client again from the server. The client connects to the server alright, but it's when it's waiting for a response that it throws an IOException. I have tried connecting my chat client to other chat servers, hence I'm sure the fault is in the chat server implementation.

I'm guessing the "villain of the piece" is this method presented below that takes the input from the connected client and sends it back, but I'm not sure why it doesn't work.

private void processClientRequest(Socket clientSocket) throws IOException {
    InputStream in = clientSocket.getInputStream();
    PrintWriter out = 
        new PrintWriter(clientSocket.getOutputStream());
    long time = System.currentTimeMillis();

    out.write("Server - " + time + ": " + in);

    out.close();
    in.close();
}

Please tell me if this method isn't the issue and you need other parts of my code instead. Thanks in advance!

Edit: I have now managed to get my server to respond to the client. I did this by changing the processClientRequest method to this:

try {
    BufferedReader in =
        new BufferedReader(
            new InputStreamReader(clientSocket.getInputStream()));

    PrintWriter out = 
        new PrintWriter(clientSocket.getOutputStream());

    long time = System.currentTimeMillis();

    out.write("Server - " + time + ": " + in.readLine());

    out.close();

    try {
        in.close();
    } catch (IOException e) {
        System.err.println("Couldn't close input stream");
    }
} catch(IOException e) {
        System.err.println("Got an IOException error while reading or writing from/to client");
}

But as of now my server can only respond the client once. If the client writes to the server a second time it does get a response, but instead of the clients message, it's "null". And since I want my echo server to be able to answer the client until the client shuts down or something like that, I need to figure out how to change that. I figure I'm going to need some kind of while loop to make this happen, but I have tried for example putting the whole try statement into an infinite while loop, but that just gave me loads of IOExceptions.

Upvotes: 1

Views: 267

Answers (1)

tgkprog
tgkprog

Reputation: 4598

You're not reading the clients input. You're just passing the toString to your out. You need to make a while loop and read from in. Maybe in a seperate thread unless you're sure the input is short. In test code should be okay:

    private void processClientRequest(Socket clientSocket) throws IOException {
        InputStream in = clientSocket.getInputStream();//wrap this in a object stream or other to read lines/ utf
        int i = 0;
        while(i++ < 1000 && in.available() > 0){
          int read = in.read();//use it if u want, like to a string builder declared out of loop and echo it back after u read input
         }
        PrintWriter out = 
        new PrintWriter(clientSocket.getOutputStream());
        long time = System.currentTimeMillis();

        out.write("Server - " + time + ": " + in);

        out.close();//should be in seperate try catches so if 1 close fails u still close other and finally close socket in 3rd try catch
        in.close();
}

Socket server with working echo server, mini web server and helpful in many more ways.

Upvotes: 1

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