iPerf3 is a tool for active measurements of the maximum achievable bandwidth on IP networks. It allows testing of TCP and UDP performance and provides detailed statistics such as throughput, retransmissions, packet loss, and jitter.

This tutorial was tested on Windows Server 2019, 2022, and 2025, but it should also work on other modern Windows Server versions.

Connect to your Windows VPS via RDP.

You will also need another device or a VPS to run some tests (testing inbound speed)

To download iPerf3, visit:

https://files.budman.pw/

Download the latest Windows 64 bit ZIP archive. Just click on it, to start downloading.

In our case, we will install iperf3.20:

Extract it to a known location, for example:

No installer is required. iPerf3 is a standalone executable.

Open Command Prompt as Administrator:

Navigate to the folder where iPerf is installed:

Check the version:

Example output:

This confirms iPerf3 is ready to use.

By default, Windows Server blocks inbound connections. To use iPerf3 in server mode, port 5201 TCP must be allowed.

Open Windows Firewall configuration by searching for Windows Defender Firewall with Advanced Security (do not confuse with Windows Defender FIrewall):

Then select "Inbound Rules" and on the right side of the window, click "New Rule...".

In the next window, select "Port" and click "Next":

Then, select TCP and enter port 5201:

Allow the connection:

Select all three: Domain, Private, Public:

Enter name for your rule and click "Finish":

Your new rule should appear in the list with status Enabled=Yes:

To allow other systems to test connectivity to your Windows VPS, start iPerf3 in server mode.

From Command Prompt:

Example output:

The server will now wait for incoming connections.

To stop the server, press Ctrl + C on your keyboard.

The interrupt message shown is normal behavior.

Inbound speed testing is critical when users report slow downloads or poor RDP file transfers.

Start iPerf3 server on Windows as shown in the previous step:

Connect from a remote Linux or Windows system (write the actual IP of your server instead of your_VPS_IP):

Then, on your Windows VPS you should see:

The example from this screenshot shows iPerf3 running in server mode on a Windows VPS and handling an inbound test from a remote client. The server listens on the default port 5201 and receives traffic for about 10 seconds, with a steady throughput of roughly 95–96 Mbit/sec. The results are consistent, with no errors or drops, and a total of 116 MB received. This indicates stable and healthy inbound network performance, meaning any remaining performance issues are likely not caused by the network itself.

To test outbound network performance, connect from your Windows VPS to a remote iPerf3 server.

or:

You can find a list of public iPerf3 servers here.

For example:

This measures how fast your Windows server can send data.

This screenshot shows an outbound iPerf3 test from a Windows VPS to a public server. The test runs for 10 seconds and quickly stabilizes at around 95 Mbit/sec after a slower first second. About 108 MB of data is transferred at roughly 90 Mbit/sec overall, which indicates stable and normal outbound network performance with no visible issues.

Testing only one direction can hide real issues. Using -R lets you validate both inbound and outbound paths without changing where the server is running.

This will allow to measure download speed to your Windows VPS by sending traffic from the Windows server to the remote client.

First, start iPerf3 server on your Windows VPS:

Then, run this command from a remote system:

On your Windows VPS, you will see the result.

To see all available options and parameters, run:

iPerf3 is the fastest and most reliable way to investigate network and performance issues on your VPS. Always test both inbound and outbound directions and avoid drawing conclusions from a single test.

If iPerf3 shows full expected bandwidth, the network is not the problem.

For more information about iPerf3, visit the official website.