The four socket amigos.

What this TCP server socket-setup question tests

This is a hard networking question that probes whether a candidate knows the precise sequence and purpose of the core socket API calls required to listen for and accept TCP connections. It is the kind of question Discord and other companies building real-time, connection-heavy systems use to verify that a candidate understands the operating-system layer, not just application-level libraries.

The question demands knowledge of the socket lifecycle: from creation through binding to a local address, marking the socket as a listening endpoint, and preparing it to accept inbound connections. Candidates must recall not just the names of these calls, but their order and why each step is necessary. Getting the sequence wrong or omitting a critical call reveals gaps in foundational network programming knowledge.

• Socket creation and address-family selection
• Binding to a local address and port
• Marking a socket for passive listening
• Accepting client connections
• TCP/IP state machine and the three-way handshake