Useful shell Commands

2. Netstat

   netstat-print network connections, routing tables, interface statistics, masquerade connections, and Mul Ticast Memberships
   See Parameters:
   

   -A (All) displays all options and does not show listen related by default
   -T (TCP) displays only TCP-related options
   -U (UDP) displays only UDP-related options
   -N refuses to display aliases, showing all numbers converted to numbers.
   -l list only service status in Listen (listening)

   -P Displays the program name that establishes the associated link
   -R display routing information, routing table
   -e display extended information, such as UID, etc.
   -S statistics according to each protocol
   -C executes the netstat command every other fixed time.

   Hint: The status of listen and listening can only be seen with-a or-l
   
   NETSTAT-ANP//List all ports (including listening and not listening), display numbers without aliases, display the program name and PID for establishing RELATED links
   The above command combined with GREP:80 can be used to find a program that is using port 80.

   Specific reference: Linux netstat command detailed

4. Lsof

   lsof-list Open files
   In a Linux environment, everything is in the form of files, with files that not only access regular data, but also access to network connectivity and hardware. So, such as Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) sockets, the system assigns a file descriptor to the application in the background, regardless of the nature of the file, which provides a common interface for the interaction between the application and the underlying operating system. Because the application opens a descriptor list of files that provides a lot of information about the application itself, it is helpful to see the list through the Lsof tool for system monitoring and troubleshooting.
   Specific reference: Linux lsof detailed

6. ?

Useful shell Commands