Linux › Section J · Network applications and services › Topic J.3
Diagnostic tools and remote procedure calls
"The service is down" can mean a dozen different things: the program is not running, it listens on the wrong address, a firewall drops the packets, or the client is talking to the wrong port. A short set of tools lets you check each possibility in turn instead of guessing.
In this topic
- Work up the layers
- ss: sockets at a glance
- lsof for network connections
- Worked example: a service nobody else can reach
- tcpdump: seeing the packets
- Worked example: do the packets arrive?
- netcat: a general-purpose test client
- Port scanning with Nmap, with permission
- Remote procedure calls and rpcbind
- Common mistakes to avoid
- Key takeaways
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