Netcat (nc or ncat) is a powerful tool for network troubleshooting and testing. Today, I’ll show you how to measure link throughput between two Linux machines using Netcat.

Preconditions

Before starting, ensure that the client machine can access the server. We’ll use a client-server model, where:

  1. The server must allow connections to the designated port (firewall rules should be adjusted accordingly).
  2. The server must have a public IP or be on the same LAN as the client (physical or virtual via VPN).
  3. Connectivity can be verified using ping or Netcat itself.

To check connectivity with Netcat:

On the server:

$ ncat -l -p 12345

(Netcat listens on TCP port 12345.)

On the client:

$ ncat <server-ip> 12345

(Netcat waits for user input, which will be sent to the server and displayed there.)

If the connection works, you’re ready for the next step.

Benchmarking Network Throughput

We’ll send a bulk of data from the client to the server using /dev/zero (a special file for generating zero bytes) and measure the transfer speed.

Step 1: Prepare the Server

On the server, run:

$ ncat -l -p 12345 > /dev/null

This redirects incoming data to /dev/null (a black hole for unwanted data), preventing terminal clutter.

Step 2: Send Data from the Client

On the client, execute:

$ dd if=/dev/zero bs=1M count=1024 | ncat <server-ip> 12345

This sends 1GB (1024 blocks of 1MB each) of zero bytes to the server.

Example Output:

1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 16.2882 s, 65.9 MB/s

Here, the measured throughput is 65.9 MB/s.

Conclusion

Using Netcat and dd, you can quickly measure network throughput between two Linux machines. This method is lightweight and effective for testing network performance without additional software.

Give it a try and see how your network performs!