WebSockets support ongoing bidirectional messaging after establishment. Applications still need authentication, heartbeat, reconnection and message identity rules.
Before you start
You should understand clients, servers, IP addresses and ports. Follow a request through name resolution, connection establishment and application exchange. Distinguish protocol guarantees from deployment policy, and use observations from the relevant layer rather than guessing from one browser error message.
The practical goal is to reason through this situation: A client reconnects after a network change and resynchronizes missed state. Read the walkthrough first, then try the interview exercise before opening its answer. The important part is explaining the decision and its consequences, rather than remembering a definition alone.
Step-by-step walkthrough
Step 1: Authenticate and own the session
Long-lived connections need bounded lifetime and permission policy.
Step 2: Detect disconnection
Heartbeat and reconnect behavior must fit infrastructure limits.
Step 3: Resynchronize application state
A new connection does not automatically contain missed events.
Worked scenario
A client reconnects after a network change and resynchronizes missed state.
A dashboard disconnects while events 40 and 41 occur. Reconnecting at event 42 leaves its state incomplete unless the protocol supports replay or a fresh authoritative snapshot. Sequence markers also help detect duplicate replayed events; reconnecting transport alone cannot establish business-state continuity.
Common mistake
A reconnected socket does not automatically replay lost business events.
Verify the behavior
Drop the connection, generate missed events and verify convergence without duplicates.
Interview exercise
Recover a live dashboard.
Answer and reasoning
Use a resume marker or authoritative snapshot and handle duplicate messages before continuing updates.
Continue learning
Compare the scenario with the Networking interview questions and test your understanding with the Networking MCQs. For terminology and implementation details, consult the reference material.