๐ถ Build a Local Network Speed-Test Tool
๐๐จ๐ข๐ง ๐๐จ๐ฆ๐ฆ๐ฎ๐ง๐ข๐ญ๐ฒ - ๐๐๐๐๐ ๐๐๐๐Want to know the actual speed between two devices on your Wi-Fi network instead of testing your Internet connection?
You can create your own simple speed-test website using Python + Flask. One device acts as the local server, while another device opens the webpage and measures download/upload speed.
For serious network benchmarking, tools such as iPerf3 are designed specifically for active bandwidth measurements.
This tutorial builds a browser-based version that is easy to understand and run on Android, Windows, Linux, or macOS.
๐งฐ What You Need
- Android phone, PC, or laptop
- Python
- Flask
- Two devices on the same Wi-Fi
- Web browser
Example:
๐ฑ Phone โ Wi-Fi Router โ ๐ป Laptop
The server can run on either device.
1๏ธโฃ Install Python
If you're using Android with Termux:
Install Termux from:
https://github.com/termux/termux-app
Then run:
pkg update pkg install python
Check:
python --version
On Windows/macOS/Linux, install Python from:
2๏ธโฃ Create the Project
In Termux:
mkdir ~/speedtest cd ~/speedtest
Create the application:
nano app.py
3๏ธโฃ Install Flask
Run:
pip install flask
Flask provides the web routes and request handling needed for our small local application. Its documentation also supports handling uploaded files through request.files, which is useful for the upload-speed test.
4๏ธโฃ Create the Speed-Test Server
Put this inside app.py:
from flask import Flask, request, Response, render_template_string
import time
app = Flask(__name__)
HTML = """
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1">
<title>Local Network Speed Test</title>
<style>
body {
margin: 0;
font-family: Arial, sans-serif;
background: #101828;
color: white;
}
.container {
max-width: 650px;
margin: auto;
padding: 25px;
}
h1 {
text-align: center;
}
.card {
background: #1d2939;
border-radius: 18px;
padding: 25px;
margin-top: 20px;
}
button {
width: 100%;
padding: 15px;
margin-top: 12px;
border: 0;
border-radius: 10px;
font-size: 17px;
cursor: pointer;
}
.result {
text-align: center;
font-size: 32px;
margin-top: 20px;
}
.small {
color: #98a2b3;
text-align: center;
}
</style>
</head>
<body>
<div class="container">
<h1>๐ถ Local Speed Test</h1>
<p class="small">
Test the connection between two devices on your local network.
</p>
<div class="card">
<h2>โฌ๏ธ Download</h2>
<button onclick="downloadTest()">
Start Download Test
</button>
<div id="download" class="result">โ</div>
</div>
<div class="card">
<h2>โฌ๏ธ Upload</h2>
<button onclick="uploadTest()">
Start Upload Test
</button>
<div id="upload" class="result">โ</div>
</div>
</div>
<script>
async function downloadTest() {
const output = document.getElementById("download");
output.innerText = "Testing...";
const start = performance.now();
const response = await fetch("/download?size=100");
const data = await response.arrayBuffer();
const end = performance.now();
const seconds = (end - start) / 1000;
const megabits =
(data.byteLength * 8) / seconds / 1000000;
output.innerText =
megabits.toFixed(2) + " Mbps";
}
async function uploadTest() {
const output = document.getElementById("upload");
output.innerText = "Testing...";
const size = 50 * 1024 * 1024;
const data = new Uint8Array(size);
const start = performance.now();
await fetch("/upload", {
method: "POST",
body: data
});
const end = performance.now();
const seconds = (end - start) / 1000;
const megabits =
(size * 8) / seconds / 1000000;
output.innerText =
megabits.toFixed(2) + " Mbps";
}
</script>
</body>
</html>
"""
@app.route("/")
def index():
return render_template_string(HTML)
@app.route("/download")
def download():
size_mb = min(
int(request.args.get("size", 100)),
500
)
total_bytes = size_mb * 1024 * 1024
chunk = b"0" * (1024 * 1024)
def generate():
remaining = total_bytes
while remaining > 0:
amount = min(
len(chunk),
remaining
)
yield chunk[:amount]
remaining -= amount
return Response(
generate(),
mimetype="application/octet-stream"
)
@app.route("/upload", methods=["POST"])
def upload():
received = 0
while True:
chunk = request.stream.read(1024 * 1024)
if not chunk:
break
received += len(chunk)
return {
"received_bytes": received
}
if __name__ == "__main__":
app.run(
host="0.0.0.0",
port=8000,
threaded=True
)
Save the file.
5๏ธโฃ Start the Server
Run:
python app.py
You should see something similar to:
Running on http://127.0.0.1:8000 Running on http://192.168.1.25:8000
The exact IP will be different on your network.
6๏ธโฃ Test It on the Same Phone
Open your browser:
http://127.0.0.1:8000
You'll see:
๐ถ Local Speed Test โฌ๏ธ Download [ Start Download Test ] โฌ๏ธ Upload [ Start Upload Test ]
7๏ธโฃ Find Your Local IP
On Android/Termux:
ip addr
Find the Wi-Fi IPv4 address.
For example:
192.168.1.25
8๏ธโฃ Connect Your Second Device
Connect your laptop/second phone to the same Wi-Fi network.
Open:
http://192.168.1.25:8000
Now the browser on the second device is communicating directly with your local server.
9๏ธโฃ Run the Download Test
Tap:
Start Download Test
The browser downloads a generated test payload from the server.
The JavaScript measures:
Downloaded bytes
รท
Elapsed time
โ
Mbps
Example:
โฌ๏ธ Download 287.42 Mbps
This is a local-network measurement, not your Internet speed.
๐ Run the Upload Test
Tap:
Start Upload Test
The browser generates a 50 MB payload and sends it to the server.
Example:
โฌ๏ธ Upload 214.73 Mbps
Again, this measures the connection between the two devices.
1๏ธโฃ1๏ธโฃ Why Local Testing Is Useful
Suppose your Internet speed is:
Internet 500 Mbps
But transferring a file between your phone and laptop is only:
35 Mbps
The problem could be somewhere in your local Wi-Fi connection, rather than your Internet connection.
A local test helps separate:
Internet speed
โ
ISP / Internet
from:
Local speed
โ
Phone โ Wi-Fi โ Router โ Laptop
1๏ธโฃ2๏ธโฃ Test Different Locations
Try the same test while moving your phone:
๐ Next to router ๐ Same room ๐ Another room ๐ Behind walls ๐ Farther from router
Record the results.
You might see something like:
Near Router Download: 620 Mbps Another Room Download: 310 Mbps Far Room Download: 95 Mbps
This gives you a simple picture of Wi-Fi performance around your home.
1๏ธโฃ3๏ธโฃ Test Different Devices
You can use:
Android โ Laptop Laptop โ Android Android โ Android Laptop โ Laptop
The same server can be used for multiple tests.
1๏ธโฃ4๏ธโฃ Add Ping Testing
You can also add a simple endpoint:
@app.route("/ping")
def ping():
return "pong"
Then JavaScript can repeatedly request:
/ping
and calculate the response time.
Example:
Ping: 8 ms
Lower latency generally means a more responsive connection.
1๏ธโฃ5๏ธโฃ Add a Live Test Screen
You can improve the interface to show:
โโโโโโโโโโโโโโโโโโโโโโโโโโโ โ ๐ถ Local Speed Test โ โ โ โ 287 Mbps โ โ Download โ โ โ โ 214 Mbps โ โ Upload โ โ โ โ 8 ms โ โ Ping โ โโโโโโโโโโโโโโโโโโโโโโโโโโโ
You can also add an animated speedometer later.
1๏ธโฃ6๏ธโฃ Important Accuracy Point
This browser-based project is great for learning and quick local comparisons, but don't treat a single result as laboratory-grade network benchmarking.
Your result can be affected by:
- Wi-Fi signal
- Router performance
- Phone CPU
- Browser
- Server CPU
- Background downloads
- Wi-Fi congestion
- Network configuration
For more rigorous bandwidth testing, iPerf3 is specifically designed for active network bandwidth measurements and supports TCP/UDP testing and reporting.
1๏ธโฃ7๏ธโฃ Try iPerf3 for Advanced Testing
If you want a more professional command-line test, install iPerf3 on two compatible devices.
On the server:
iperf3 -s
On the client:
iperf3 -c 192.168.1.25
The official iPerf documentation uses this client/server model and supports options such as test duration, parallel streams, TCP/UDP, and JSON output.
Official website:
1๏ธโฃ8๏ธโฃ Add Multiple Test Sizes
Instead of always testing 100 MB, create:
Quick Test 25 MB Normal Test 100 MB Large Test 500 MB
This lets you compare short and longer transfers.
1๏ธโฃ9๏ธโฃ Add Test History
Store results like:
23 Sep Download: 612 Mbps Upload: 438 Mbps Ping: 7 ms 24 Sep Download: 574 Mbps Upload: 421 Mbps Ping: 9 ms
Then display them as a simple graph.
2๏ธโฃ0๏ธโฃ Stop the Server
When you're finished:
CTRL + C
The local speed-test website will stop.
๐ Final Result
Your setup becomes:
๐ถ Wi-Fi
โ
โโโโโโโโโโโดโโโโโโโโโโ
โ โ
๐ฑ Android ๐ป Laptop
Python/Flask Browser
โ โ
โโโโโ Speed Test โโโโ
And the browser can show:
๐ถ LOCAL NETWORK SPEED โฌ๏ธ Download 287.42 Mbps โฌ๏ธ Upload 214.73 Mbps ๐ก Ping 8 ms
๐ Useful Links
Python:
Flask:
https://flask.palletsprojects.com/
Python HTTP Server Documentation:
https://docs.python.org/3/library/http.server.html
iPerf3:
iPerf3 Documentation:
https://iperf.fr/iperf-doc.php
Termux:
https://github.com/termux/termux-app
Note: Keep this server on your trusted local network. Python's basic http.server is explicitly not intended for production use; this project is for local testing and learning.ย