Network I/O (Input/Output) is a critical aspect of system performance, particularly for applications that rely heavily on network communication. Monitoring and managing network I/O can help you understand bandwidth usage, detect potential bottlenecks, and ensure the smooth operation of network-dependent applications. In the Apple environment, particularly on macOS, there are several tools and commands available to monitor and manage network I/O effectively.

This article will guide you through the process of monitoring network I/O on macOS using built-in tools and commands. We will cover practical examples using Terminal commands and graphical tools that are native to the macOS environment.

Examples:

1. Using nettop Command: The nettop command provides a real-time display of network usage by processes. It is a powerful tool for monitoring network I/O at a granular level.

   # Open Terminal and run the following command to start nettop
   nettop

   This command will display a real-time table of network usage, showing data sent and received by each process.

2. Using iftop Command: While not pre-installed, iftop is a useful tool for monitoring bandwidth usage. You can install it using Homebrew.

   # Install Homebrew if you haven't already
   /bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/HEAD/install.sh)"
   
   # Install iftop using Homebrew
   brew install iftop
   
   # Run iftop to monitor network traffic
   sudo iftop

   iftop will display a list of network connections and the bandwidth usage for each.

3. Using Activity Monitor: Activity Monitor is a graphical tool that comes pre-installed on macOS. It provides a user-friendly interface to monitor various system metrics, including network usage.

   • Open Activity Monitor from the Applications > Utilities folder.
   • Click on the "Network" tab.
   • You will see columns for "Sent Bytes" and "Received Bytes," which show the amount of data being sent and received by each process.

4. Using netstat Command: The netstat command provides various network statistics and information about network connections.

   # Display network interface statistics
   netstat -i
   
   # Display routing table information
   netstat -r
   
   # Display all active network connections
   netstat -an

   These commands will provide detailed information about network interfaces, routing tables, and active connections.