Random Musings

In the context of the netstat and ss commands, the terms LISTEN and LISTENING refer to the state of a socket that is waiting for incoming connections, but there is a subtle difference in how they are presented in the output of each command:

1. LISTEN in netstat

• In netstat, the LISTEN state indicates that a socket is open and ready to accept incoming connections. This state is shown for listening TCP sockets, which are waiting for a connection request from a remote host.
• Usage Example: You would typically see LISTEN in the output when using the netstat -a or netstat -tuln command to display all active connections and listening ports. Example output from netstat: Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN Here, the socket is listening on port 80 for incoming connections on any network interface.

2. LISTENING in ss

• In ss, LISTENING is used instead of LISTEN to describe the state of a socket that is waiting for incoming connections. Essentially, LISTENING means the same as LISTEN in netstat, but ss uses a more descriptive term for the socket state.
• Usage Example: When you run ss -a or ss -tuln to display listening ports and connections, LISTENING will be shown for sockets that are in this waiting state. Example output from ss: State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 128 0.0.0.0:80 0.0.0.0:* Again, this indicates a socket that is listening for connections on port 80.

Key Differences:

• Terminology:
  • netstat uses LISTEN, while ss uses LISTENING to describe the state of a socket waiting for incoming connections.
• Context: The meaning is effectively the same; both represent sockets that are open and waiting for connection requests. The difference is primarily in the naming convention between the two tools.

In summary:

• LISTEN in netstat = LISTENING in ss (both indicate the same state for TCP sockets waiting for incoming connections).