How do I Find the PID of a Process Using a Specific Port

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Introduction:

Understanding and managing processes on a computer system is a crucial skill for system administrators and developers. One common challenge is identifying the process ID (PID) associated with a specific port, especially in networking scenarios. This guide will unravel the mystery, providing you with practical insights into finding the PID of a process using a specific port on your Linux system.

Finding the PID of a Process Using a Specific Port:
Using lsof (List Open Files) Command:

The lsof command is a powerful tool for listing open files and processes on a Unix-like system. Here’s how you can use it to find the PID associated with a specific port:

  1. Basic Usage:
    lsof -i :<port_number>
    Replace <port_number> with the specific port you want to investigate. This command provides detailed information about processes using the specified port.

    Example: lsof -i :8080
  2. Filtering Output for PID Only:
    lsof -t -i :<port_number>
    The -t option extracts only the PIDs from the output, making it more suitable for scripting or further processing.
    Example: lsof -t -i :8080
Using netstat Command:

The netstat command provides information about network connections. While it may not be as detailed as lsof, it can still be useful for finding PIDs associated with ports.

  1. Basic Usage:
    netstat -tulpn | grep :<port_number>
    This command shows listening ports along with their associated PIDs.
    Example: netstat -tulpn | grep :8080
Example Scenarios:
  1. Finding PID for Port 8080:
    lsof -i :8080
    This command may return output similar to:
    COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
    nginx 1234 user 10u IPv4 12345 0t0 TCP *:8080 (LISTEN)
  2. Extracting PID Only for Port 8080:
    lsof -t -i :8080
    This command returns only the PID:
    1234
  3. Using netstat for Port 8080:
    netstat -tulpn | grep :8080
    The output might resemble:
    tcp6 0 0 :::8080 :::* LISTEN 1234/nginx
Conclusion:

Identifying the PID of a process using a specific port is an essential skill for system administrators and developers. By leveraging commands like lsof and netstat, you gain valuable insights into the processes interacting with your system’s network. Whether you’re troubleshooting network issues or managing processes, these techniques will prove invaluable in your Linux journey.