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Chat (part 16)

Java Multithreading, Level 6, Lesson 15

Resolved

I tried with different if else configurations (and if else if also) and I don't understand why it's not working...

Now everything is ready for us to add the necessary methods to the SocketThread class.

1) Add a protected clientHandshake() throws IOException, ClassNotFoundException method. This method will represent the client to the server.
It must:
a) In a loop, use the connection field to receive messages.
b) If a received message is a NAME_REQUEST (the server has requested a name), use the getUserName method to ask the user to enter a username, create a new message that is a MessageType.USER_NAME and contains the entered name, and send the message to the server.
c) If a received message is a MessageType.NAME_ACCEPTED (the server has accepted the name), it means the server has accepted the client name, and you need to inform the main thread, which is eagerly waiting for this news. Do this by passing true to the notifyConnectionStatusChanged() method. Then exit the method.
d) If there is a message of any other type, throw an IOException("Unexpected MessageType").

2) Add a protected void clientMainLoop() throws IOException, ClassNotFoundException method. This method will implement the server's main message-processing loop. Inside the method:
a) Use the connection field to receive a message from the server.
b) If it is a text message (MessageType.TEXT), process it using the processIncomingMessage() method.
c) If the message is a MessageType.USER_ADDED, process it using the informAboutAddingNewUser() method.
d) If the message is a MessageType.USER_REMOVED, process it using the informAboutDeletingNewUser() method.
e) If the client receives a message of some other type, throw an IOException("Unexpected MessageType").
f) Put the code from the previous steps in an infinite loop. The loop will terminate automatically if an error (exception) occurs or the thread on which the loop is running is interrupted.

Requirements:

The clientHandshake() method should use the connection field to send a new message (MessageType.USER_NAME, getUserName()) if the received message is a MessageType.NAME_REQUEST.
The clientHandshake() method should call notifyConnectionStatusChanged(true) and terminate if the received message is a MessageType.NAME_ACCEPTED.
The clientHandshake() method should throw an IOException if the received message is not a MessageType.NAME_ACCEPTED or a MessageType.NAME_REQUEST.
The clientHandshake() method should receive messages from the server as long as the message type is MessageType.NAME_REQUEST.
The clientMainLoop() method should receive messages from the server as long as the message type is MessageType.TEXT, MessageType.USER_REMOVED, or MessageType.USER_ADDED.
The clientMainLoop() method must process the received message using the processIncomingMessage() method if the received message is a MessageType.TEXT.
The clientMainLoop() method must process the received messages using the informAboutAddingNewUser() method if the received message is a MessageType.USER_ADDED.
The clientMainLoop() method must process the received messages using the informAboutDeletingNewUser() method if the received message is a MessageType.USER_REMOVED.
The clientMainLoop() method should throw an IOException if the received message is not a MessageType.TEXT, MessageType.USER_REMOVED, or MessageType.USER_ADDED.

package com.codegym.task.task30.task3008; import java.net.*; import java.util.*; import java.util.concurrent.ConcurrentHashMap; import java.io.IOException; public class Server { private static Map<String, Connection> connectionMap = new ConcurrentHashMap<String, Connection>(); public static void sendBroadcastMessage(Message message) { Iterator<Connection> valueIterator=connectionMap.values().iterator(); while(valueIterator.hasNext()){ try{ valueIterator.next().send(message); } catch (IOException e){ System.out.println("Message couldn't be sent"); } } } public static void main (String[] args){ int port = ConsoleHelper.readInt(); ServerSocket serverSocket = null; try{ serverSocket= new ServerSocket(port); System.out.println("Server is running"); while (true){ Socket s = serverSocket.accept(); Thread thread = new Handler(s); thread.start(); } } catch (Exception e){ System.out.println(e.getMessage()); try{ serverSocket.close(); }catch (Exception ex){ ex.printStackTrace(); } } } private static class Handler extends Thread{ private Socket socket; public Handler (Socket socket){ this.socket = socket; } private String serverHandshake(Connection connection) throws IOException, ClassNotFoundException { boolean nameRequestOk = true; boolean isAlreadyTaken = false; Message response = null; boolean isKeyPresent = false; while (nameRequestOk) { connection.send(new Message(MessageType.NAME_REQUEST)); response = connection.receive(); if (response.getType().equals(MessageType.USER_NAME)){ if (!response.getData().equals("")){ isKeyPresent = connectionMap.containsKey(response.getData()); if (!isKeyPresent){ connectionMap.put(response.getData(), connection); connection.send(new Message(MessageType.NAME_ACCEPTED)); nameRequestOk = false; } } } } return response.getData(); } private void notifyUsers(Connection connection, String userName) throws IOException { String name = userName; for (Map.Entry<String, Connection> entry : connectionMap.entrySet()){ if( entry.getKey() != userName) { connection.send(new Message(MessageType.USER_ADDED, entry.getKey())); } } } private void serverMainLoop(Connection connection, String userName) throws IOException, ClassNotFoundException { while (true) { try { Message received = connection.receive(); if (received.getType().equals(MessageType.TEXT)) { String m = userName + ": " + received.getData(); sendBroadcastMessage(new Message(MessageType.TEXT, m)); } else { String error = "not text error"; ConsoleHelper.writeMessage(error); } } catch (Exception e) { ConsoleHelper.writeMessage(e.getMessage()); } } } @Override public void run(){ ConsoleHelper.writeMessage("New connection using " +socket.getRemoteSocketAddress()+" is established."); String newClient=""; Connection connection=null; try { connection = new Connection(socket); newClient = serverHandshake(connection); sendBroadcastMessage(new Message(MessageType.USER_ADDED, newClient)); notifyUsers(connection, newClient); serverMainLoop(connection, newClient); connectionMap.remove(newClient); sendBroadcastMessage(new Message(MessageType.USER_REMOVED, newClient)); connection.close(); }catch (IOException i){ if(newClient != ""){ connectionMap.remove(newClient); sendBroadcastMessage(new Message(MessageType.USER_REMOVED, newClient)); try{ connection.close(); }catch (IOException y){ } } }catch (ClassNotFoundException c){ if(newClient != ""){ connectionMap.remove(newClient); sendBroadcastMessage(new Message(MessageType.USER_REMOVED, newClient)); try{ connection.close(); }catch (IOException y){ } } }catch (Exception e){ if(newClient != ""){ connectionMap.remove(newClient); sendBroadcastMessage(new Message(MessageType.USER_REMOVED, newClient)); try{ connection.close(); }catch (IOException y){ } } } } } }

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Potato Sheep

Level 3 , Sampaloc, Philippines

14 September 2019, 01:48

Is this okay now? I can help you if you want.

Nicolas Huet

Level 41 , Provins, France

14 September 2019, 12:41

Yes I have resolved it finally, thank you :)

Niladri pradhan

Level 33 , Mumbai, India

28 November 2019, 14:01

please help

Nicolas Huet

Level 41 , Provins, France

12 September 2019, 14:36

solution

Ok resolved it. Hint for those who are stuck : Dont forget to check is you are already connected or not...! The rest is good placements of checks.

Niladri pradhan

Level 33 , Mumbai, India

28 November 2019, 14:04

where to check if connected or not

Alexandre Lalancette

Level 41 , Quebec, Canada

17 January 2020, 20:10

What is the issue? I'm stuck at the same place!

Nicolas Huet

Level 41 , Provins, France

12 September 2019, 13:58

public class SocketThread extends Thread {
        protected void clientHandshake() throws IOException, ClassNotFoundException {
            while (true) {
                Message message = connection.receive();
                if (message.getType() != MessageType.NAME_REQUEST && message.getType() != MessageType.NAME_ACCEPTED){
                    throw new IOException("Unexpected MessageType");
                }

                if (message.getType().equals(MessageType.NAME_REQUEST)){
                    connection.send(new Message (MessageType.USER_NAME, getUserName()));
                      continue;
                }

                if (message.getType().equals(MessageType.NAME_ACCEPTED)){
                        notifyConnectionStatusChanged(true);
                        break;
                }
            }

        }
        protected void clientMainLoop() throws IOException, ClassNotFoundException{
            while (true) {
                    Message message = connection.receive();
                    if (message.getType() != MessageType.TEXT && message.getType() != MessageType.USER_REMOVED && message.getType() != MessageType.USER_ADDED){
                    throw new IOException("Unexpected MessageType");
                    }
                    if (message.getType().equals(MessageType.TEXT)) {
                        processIncomingMessage(message.getData());
                        continue;
                    }if (message.getType().equals(MessageType.USER_ADDED)) {
                        informAboutAddingNewUser(message.getData());
                        continue;
                    }if (message.getType().equals(MessageType.USER_REMOVED)) {
                        informAboutDeletingNewUser(message.getData());
                    }

            }
        }

this passes everything, UNLESS the very first condition! wich is very odd...