A professional WPF-based network diagnostic tool for testing bandwidth, latency, jitter, and detecting network asymmetry issues. Built for IT professionals and MSPs to quickly diagnose network performance problems.
- Multi-threaded speed tests - Saturate 10G/25G/40G+ links
- Bidirectional mode - Test upload and download simultaneously
- Real-time statistics - Live MB/s and Mbps display
- Asymmetry detection - Automatically warns when upload/download speeds differ >20%
- Configurable parameters - Threads, duration, port, buffer size
- RTT measurement - Min/avg/max round-trip time
- Jitter calculation - Inter-packet variation for VoIP troubleshooting
- Packet loss detection - Identify network reliability issues
- Color-coded results - Green/yellow/red status indicators
- HTML reports - Beautiful, customer-ready diagnostic reports
- Interactive graphs - Chart.js visualizations of throughput over time
- At-a-glance verdict - "Network Healthy" or "Issues Detected"
- Dual graph views - Both Mbps and MB/s representations
- Asymmetry highlighting - Red warnings for NIC/driver issues
- Bandwidth validation - Verify 10G/25G/40G infrastructure performance
- NIC troubleshooting - Detect driver bugs and buffer tuning issues
- VoIP diagnostics - Measure jitter and packet loss for phone systems
- Switch CPU issues - Identify forwarding plane problems
- Customer proof - Professional reports showing network performance
- Download the latest
NetworkSpeedTest.exefrom Releases - Copy to any Windows 10/11 machine
- Run - no installation required
- File size: ~70MB (self-contained, no dependencies)
Requirements:
- Visual Studio 2022 or later
- .NET 6.0 SDK or later
Steps:
git clone https://github.com/yourusername/network-speed-test.git
cd network-speed-test
dotnet restore
dotnet build -c ReleasePublish as single executable:
dotnet publish -c Release -r win-x64 --self-contained true -p:PublishSingleFile=true -p:EnableCompressionInSingleFile=true -p:IncludeNativeLibrariesForSelfExtract=trueOutput: bin\Release\net6.0\win-x64\publish\NetworkSpeedTest.exe
On Server Machine:
- Launch
NetworkSpeedTest.exe - Click Server Mode tab
- Click Start Test
- Server listens on port 5201
On Client Machine:
- Launch
NetworkSpeedTest.exe - Click Client Mode tab
- Enter server IP address
- Check Bidirectional (recommended)
- Click Start Test
- Wait for test to complete
- Click Generate Report for HTML output
- Click Latency Test tab
- Enter target IP address
- Set duration (e.g., 300 seconds for 5 minutes)
- Click Start Latency Test
- View real-time RTT, jitter, and packet loss
- Click Generate Report for detailed analysis
| Link Speed | Threads | Buffer Size |
|---|---|---|
| 1 Gbps | 4 | 128 KB |
| 10 Gbps | 8 | 256 KB |
| 25 Gbps | 12 | 512 KB |
| 40 Gbps | 16 | 512 KB |
| 100 Gbps | 32 | 1024 KB |
Windows Firewall:
New-NetFirewallRule -DisplayName "Network Speed Test Server" -Direction Inbound -Protocol TCP -LocalPort 5201 -Action Allow- <10% difference → Normal, network is healthy ✅
- 10-20% difference → Minor asymmetry, investigate if causing issues
⚠️ - >20% difference → Significant problem, likely NIC/driver issue ❌
Example:
- Download: 9.2 Gbps
- Upload: 7.5 Gbps
- Asymmetry: 18% → Check NIC offload settings
- NIC offload settings - TCP Checksum, Large Send Offload (LSO), Receive Side Scaling (RSS)
- Outdated drivers - Especially Realtek, older Intel/Broadcom drivers
- Buffer mismatches - Send vs receive buffer configuration
- Flow control - Switch-level pause frame issues
| Metric | Good | Acceptable | Poor |
|---|---|---|---|
| Latency | <30ms | 30-100ms | >100ms |
| Jitter | <10ms | 10-30ms | >30ms |
| Packet Loss | 0% | <0.5% | >1% |
For VoIP: Keep latency <30ms, jitter <10ms, packet loss <0.1%
- Verify server is running in Server mode
- Check firewall rules on both machines
- Confirm port 5201 is not blocked
- Test connectivity:
Test-NetConnection -ComputerName <target> -Port 5201
- Increase thread count (try 12-16 threads)
- Increase buffer size (512 KB or 1024 KB)
- Check for network bottlenecks (switches, cables, NICs)
- Disable antivirus temporarily for testing
- Verify NIC is running at full speed (check link status)
Step 1: Check NIC offload settings (both machines):
Get-NetAdapterAdvancedProperty -Name "Ethernet*" | Where-Object {$_.DisplayName -like "*Offload*"}Step 2: Update NIC drivers:
Get-NetAdapter | Select-Object Name, DriverVersion, DriverDateDownload latest from manufacturer website.
Step 3: Try different buffer sizes:
# Test with 128 KB, 256 KB, 512 KB, 1024 KBStep 4: Reset TCP/IP stack (last resort):
netsh int ip reset
netsh winsock reset
# Reboot requiredScenario: Customer claims new 10G connection is slow
Test Results:
- Download: 9.2 Gbps ✅
- Upload: 9.1 Gbps ✅
- Asymmetry: 1% ✅
- Latency: 0.5ms ✅
Conclusion: Network is performing perfectly. Problem is elsewhere (disk I/O, application, etc.)
Scenario: Phone calls sound choppy, dropping
Test Results:
- Bandwidth: 950 Mbps ✅
- Latency: 85ms
⚠️ - Jitter: 45ms ❌
- Packet Loss: 2.3% ❌
Conclusion: Switch CPU overload or congestion. Check switch forwarding plane, upgrade switch, or implement QoS.
Scenario: File uploads to server are slow, downloads are fast
Test Results:
- Download: 9.2 Gbps ✅
- Upload: 2.1 Gbps ❌
- Asymmetry: 77% ❌
Conclusion: Severe NIC asymmetry. Updated Intel driver from v12 to v25. Retest: Both directions now 9+ Gbps ✅
- Language: C# (.NET 6.0)
- UI Framework: WPF (Windows Presentation Foundation)
- Networking: Native TCP sockets with async/await
- Threading: Real multi-threading (no PowerShell jobs)
- Reporting: HTML + Chart.js for interactive graphs
- Transport: TCP for reliability
- Default Port: 5201 (configurable)
- Server: Sends continuous data stream
- Client: Receives and measures throughput
- Bidirectional: Simultaneous send/receive on same connections
- Latency: TCP echo with timestamp measurement
- Tested up to: 100 Gbps localhost
- Typical overhead: <1% CPU per thread
- Memory usage: ~50-100MB
- Report generation: <1 second
- Upload
NetworkSpeedTest.exeto software repository - Deploy to technician machines
- No installation or admin rights required
- Reports save to configurable location (default:
Desktop\SpeedTestReports)
# Copy to Program Files
Copy-Item "NetworkSpeedTest.exe" "C:\Program Files\NetworkTools\"
# Create desktop shortcut
$WshShell = New-Object -ComObject WScript.Shell
$Shortcut = $WshShell.CreateShortcut("$env:Public\Desktop\Network Speed Test.lnk")
$Shortcut.TargetPath = "C:\Program Files\NetworkTools\NetworkSpeedTest.exe"
$Shortcut.Save()Simply copy NetworkSpeedTest.exe to a USB drive. Run from any Windows 10/11 machine with no installation.
| Feature | This Tool | iperf3 | PingPlotter | Commercial Tools |
|---|---|---|---|---|
| GUI | ✅ | ❌ | ✅ | ✅ |
| Asymmetry Detection | ✅ | ❌ | ❌ | Some |
| Combined Speed+Latency | ✅ | ❌ | ❌ | Rare |
| HTML Reports | ✅ | ❌ | ✅ | ✅ |
| Windows Native | ✅ | ❌ | ✅ | ✅ |
| Free | ✅ | ✅ | ❌ | ❌ |
| Single .exe | ✅ | ❌ | ❌ | Varies |
| Customer-Ready Output | ✅ | ❌ | ✅ | ✅ |
Contributions are welcome! Please:
- Fork the repository
- Create a feature branch (
git checkout -b feature/amazing-feature) - Commit your changes (
git commit -m 'Add amazing feature') - Push to the branch (
git push origin feature/amazing-feature) - Open a Pull Request
This project is Dual licensed under the AGPL v3 + Commercial Exception - see the AGPL v3 file for details.
- Built with Claude Code by Anthropic
- Chart.js for beautiful graphs
- Inspired by iperf, but focused on real-world IT troubleshooting
- Icon design optimized for professional MSP deployment
- Issues: GitHub Issues
- Documentation: Wiki
- Discussions: GitHub Discussions
⭐ If this tool saves you time troubleshooting networks, give it a star!
Built for MSPs and IT professionals who need fast, reliable, customer-ready network diagnostics.