A Linux administrator is checking connectivity between two servers in separate subnets: Server A: 10.1.2.20 (source) Server B: 10.2.1.10 (destination on port 8080) The administrator tried to run the c

tcpdump 'tcp port 8080' passively captures packets on port 8080 but does not initiate any connection test or create a listener, so curl from Server A would still be refused.

ss -l -p dport=8080 dst 10.2.1.10 is syntactically invalid for ss and is a socket statistics display command, not a tool for creating a listener or testing a connection.

nc -l -p 8080 10.2.1.10 uses incorrect netcat syntax - pairing -l with a destination IP in this form does not correctly bind a listener to port 8080 on Server B's interface.

nmap -v -p 8080 10.2.1.10 performs a verbose port scan against Server B's own IP, actively probing whether port 8080 is open, closed, or filtered from the server's perspective. This gives the administrator a direct connection test result from Server B itself, confirming the port state and any firewall behavior. Running nmap against the local interface is a standard method to verify port accessibility and simulate the connection test.