[Linux] Bash netstat Uso: Monitor network connections and statistics

Overview

The netstat command is a powerful tool used in Linux and other Unix-like operating systems to display network connections, routing tables, interface statistics, masquerade connections, and multicast memberships. It helps users understand the current state of the network and troubleshoot connectivity issues.

Usage

The basic syntax of the netstat command is as follows:

netstat [options] [arguments]

Common Options

Here are some commonly used options with the netstat command:

• -a: Show all connections and listening ports.
• -t: Display TCP connections.
• -u: Display UDP connections.
• -n: Show numerical addresses instead of resolving hostnames.
• -l: Show only listening sockets.
• -p: Show the process ID and name of the program to which each socket belongs.
• -r: Display the routing table.

Common Examples

1. Display all active connections:

   netstat -a
   

2. Show only TCP connections:

   netstat -t
   

3. Show only listening ports:

   netstat -l
   

4. Display connections with numerical addresses:

   netstat -n
   

5. Show the process using each connection:

   netstat -p
   

6. Display the routing table:

   netstat -r
   

Tips

• Combine options for more detailed output. For example, netstat -tuln will show all listening TCP and UDP ports with numerical addresses.
• Use grep to filter results. For example, netstat -a | grep LISTEN will show only listening connections.
• Regularly monitor your network connections to identify any unauthorized access or unusual activity.