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07-logouts.md

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Lesson 7 - Notify When Users Disconnect

Goals

We know when users login, we send and receive chatroom messages.. but how do we know when users disconnect?

Let's write some code to handle disconnects and display a message *** [username] disconnected when a socket disconnects.

How will we accomplish this? With more channels, of course!

  1. Whenever a ChatUser fails to read/write to its connection socket, we will send a message on the ChatRoom.disconnect channel to notify the ListenForMessages loop that the socket has been disconnected.
  2. When such a message is received by the ChatRoom, remove it from the users map and broadcast a message to the rest of the clients saying it's disconnected.

Steps

  1. Find the ChatRoom.Logout function. Add some code that does the following:
  2. 🌟 Send the supplied username to the cr.disconnects channel.

Stuck on any of the steps above? Ask your TA, or see the solution!

  1. Update the ListenForMessages loop to handle messages on cr.disconnects:
  2. 🌟 Add a case statement that reads the username from cr.disconnects
  3. 🌟 if the username is in the cr.users map: 1. 🌟 call Close() on the ChatUser object and remove it from the map. 1. 🌟 call Broadcast to send a message: *** [username] has disconnected

Stuck on any of the steps above? Ask your TA, or see the solution!

  1. Now that we have Logout implemented, let's call Logout whenever the ChatUser read and write loops have errors reading or writing from the socket.

  2. Update ChatUser.ReadIncomingMessages so that it does the following:

1. :star2: If cu.ReadLine() returns an error, do not write a message to the `chatroom.incoming` queue. 
Instead, call `chatroom.Logout` with the current username.
1. :star2: Add some logic that checks if `cu.disconnect` is set, then exit the loop.

[Stuck on any of the steps above? Ask your TA, or see the solution!](code/07-logouts/chat.go#L115-L121)
  1. Update ChatUser.WriteOutgoingMessages so that:
1. :star2: If cu.ReadLine() returns an error, do not write a message to the queue. Instead,
call `chatroom.Logout` with the current username.
1. :star2: Add some logic that checks if `cu.disconnect` is set, then exit the loop.

[Stuck on any of the steps above? Ask your TA, or see the solution!](code/07-logouts/chat.go#L133-L141)
  1. Finally, let's implement ChatUser.Close. This will set the disconnect variable and close the socket.
func (cu *ChatUser) Close() {
	// TODO: close the socket
}
  1. 🌟 In Close(), set ChatUser.disconnect = true
  2. 🌟 Close the ChatUser.conn

Stuck on any of the steps above? Ask your TA, or see the solution!

  1. Now when a user disconnects, you'll see a disconnect message!
 $ nc localhost 6677
 Welcome to Jen's chat server!
 Please enter your username: funcuddles
 Welcome, funcuddles
 *** funcuddles just joined the chatroom
 *** bob just joined the chatroom
 hello this is dog
 [funcuddles] hello this is dog
 [bob] bye funcuddles, I gotta go!
 *** bob has disconnected