Question

I have a server that communicates with a client.

The server is multithreaded, and this thread is created with the socket and a bufferedreader connected to the socket, when the first line read from the socket is “request”:

public class scriptComm implements Runnable {

private Socket sock;
private Socket sock2;
private Connection connection;
private BufferedReader reader;

@Override
public void run() {
    try {

        String name = reader.readLine();
        String password = reader.readLine();

        String line;
        connection = methods.connectToDatabase();
        BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(sock.getOutputStream()));
        if (connection != null && name != null && password != null) {
            try {
                ResultSet rs = connection.createStatement().executeQuery(
                        "SELECT name, password, doupdate FROM accounts "
                        + "WHERE name = '" + name + "' AND doupdate = 'yes'"
                        + " AND password = '" + password + "'");
                if (rs.next()) {
                    methods.log("worked");
                    bw.write("accept");
                    bw.flush();
                    bw.close();
                    reader = new BufferedReader(new InputStreamReader(sock2.getInputStream()));
                    if ((line = reader.readLine()) != null) {
                        mainFrame.jTextArea1.append("line \n");
                        connection.createStatement().executeUpdate(
                                "UPDATE accounts SET updatetext = '" + line + "' "
                                + "WHERE name = '" + name + "'");
                    }else{
                        mainFrame.jTextArea1.append("No text received \n");
                    }
                } else {
                    bw.write("decline");
                    bw.flush();
                }
                bw.close();
                rs.close();
            } catch (SQLException ex) {
                methods.log("Error when executing statement in scriptComm");
                ex.printStackTrace();
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        } else {
            methods.log("missing values in scriptComm");

        }
    } catch (IOException ex) {
    }


}

public scriptComm(Socket sock, BufferedReader reader) {
    this.sock = sock;
    this.sock2 = sock;
    this.reader = reader;
}}

You may notice that I close the bw stream after it writes “accept”.

This is due to the client simply hanging there, as if it doesn’t receive any input, when the stream is not closed.

The client:

        try{
        String line;
        Socket sock = new Socket("myipaddresshere",portnumber); 
        PrintWriter writer = new PrintWriter(sock.getOutputStream());
        BufferedReader reader = new BufferedReader(new InputStreamReader(sock.getInputStream()));
        writer.println("script");
        writer.flush();
        writer.println(jTextField1.getText());
        writer.flush();
        writer.println(jTextField2.getText());
        writer.flush();
        if ((reader.readLine()).equals("accept")) {
            writer.write("testing123");
            writer.flush();
            writer.close();
        } else {
            jTextArea1.append("fail");

        }
        reader.close();
        writer.close();
    }catch(IOException e){
        jTextArea1.append("Server not available. Please try again later.");
    }

When the stream is not closed after writing “accept” from the server, it’s as if the client just sits at the if(reader.readLine().equals(“accept”)) boolean check ( and yes, the stream is flushed server-side ).

However, when the stream is also closed server-side, it passes the boolean check and continues on to write the line “testing123” to the stream. The server can obviously not read this line as the socket stream was closed when the BufferedReader closed. As you may notice, I tried replicating the socket by simply creating another variable called sock2, but it seems this connection closes as well (makes sense).

Note: when connecting with a wrong user/pass (i.e. when rs.next() returns false), it does write “decline” to the stream and the client gets this.

Really confused about this one..

Thanks,
Mike.

Answer 1

Note, a write doesn’t write a newline, and you are trying to read whole lines. You need to write a newline character before you flush.

Edither use BufferedWriter.newLine() or append "\n" to the strings that you write.