Initial State:

Client: client_token = false
Server: server_token = false, new_messages = false

Step 1: Client sends request

Client sends client_token = false
Message successfully received by server

Step 2: Server processes request

Server sees client_token == server_token
Sets new_messages = false
Responds with server_token = false
Response successfully received by client

Step 3: Server generates new message

Server sets server_token = true (flipped)
Sets new_messages = true

Step 4: Client sends another request

Client sends client_token = false
Message successfully received by server

Step 5: Server processes request

Server sees client_token != server_token
Keeps new_messages = true
Responds with server_token = true
This response is lost due to unreliable channel

Step 6: Client doesn't receive response

Client's state remains unchanged
client_token still false
Client is unaware of new messages

Step 7: Client sends another request

Client sends client_token = false again
Message successfully received by server

Step 8: Server processes request

Server sees client_token != server_token
Sets new_messages = false (This is the error!)
Responds with server_token = true
Response successfully received by client

Step 9: Client processes response

Client sees server_token != client_token
Client pulls messages and updates client_token = true