What are the commands to view ports in Linux?

Linux command to view ports: 1. [a] Displays all connections and listening ports of this machine; 2. [n] In the form of network IP address, displays the currently established effective connections and ports; 3. [ r] displays routing table information; 4. [s] displays statistical information by protocol; 5. [v] displays currently valid connections.

Linux command to view the port:

First type:

lsof -i:Port number

Second type:

netstat -nltp | grep port number

• - a: Display all connections and listening ports of this machine

• -n: In the form of network IP address, display the currently established effective connections and ports

• -r: Display routing table information

• -s: Display statistical information by protocol

• -v: Display currently valid connections

• -t: Display all TCP protocol connections

• -u: Display all UDP protocol connections

• -i: Display the status of the automatically configured port

• -l: Only display the service network status with the connection status of listening

• -p: Display pid/program name

Several statuses of TCP connection

• ESTABLISHED Established

• CLOSED Closed

• ##LISTENING Listening

• FIN-WAIT-2 Waiting for the connection to be closed

• TIME-WAIT Wait enough time to ensure that the server closes the connection normally

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