Testing WoL Packet Arrival Methods

Testing WoL Packet Arrival Methods | Generated by AI

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Question: How to test Wake-on-LAN? Specifically, if I manually turn on the computer, how can I check whether magic packets are actually arriving at it?

Answer:

Here are the most practical and reliable ways to verify that Wake-on-LAN magic packets are reaching the target computer (while it is already powered on):

1. Best & most direct method: Use packet capture on the target computer

While the PC is powered on and connected:

Windows

Install Wireshark (free)
Start capture on the Ethernet interface
Use capture filter: udp port 7 or udp port 9 or eth.dst == ff:ff:ff:ff:ff:ff
Send a Wake-on-LAN packet from another device
Look for packets containing your MAC address repeated 16 times after 6 bytes of FF:FF:FF:FF:FF:FF

Linux / macOS

# Quick one-liner (shows magic packets containing your MAC)
sudo tcpdump -i eth0 -n -v ether dst ff:ff:ff:ff:ff:ff and udp port 7 or udp port 9

# Or full capture and grep (recommended)
sudo tcpdump -i eth0 -w wol-test.pcap ether dst ff:ff:ff:ff:ff:ff
# then later:
tcpdump -r wol-test.pcap -X | grep -A 2 -B 2 "FF FF FF FF FF FF"

You should see something like:

FF FF FF FF FF FF  04 7c 16 d9 54 5b  ...  04 7c 16 d9 54 5b  (repeated 16 times)

If you see this pattern → the magic packet is reaching the NIC.

2. Quick method — check link/activity LED behavior (works on many NICs)

Put computer to sleep (S3) or hibernation (S4) — not full shutdown if your BIOS/NIC only listens in S5 after boot
Send WoL packet
Watch the Ethernet port LEDs on the computer:
- Many NICs (especially Realtek, some Intel) briefly blink or change pattern for 0.5–2 seconds when they receive and recognize a correct magic packet — even if the computer doesn’t actually wake (due to BIOS settings or power policy)
- This is not 100% reliable but is a very quick “did it arrive?” indicator

3. Enable WoL logging via driver / OS (less common but very clean)

Windows (some Intel & Realtek drivers):

Device Manager → Network adapters → your Ethernet → Properties → Advanced
Look for: “Wake on Magic Packet”, “Wake on Pattern Match”, “Energy Efficient Ethernet” → make sure enabled
Advanced → “Log Wake Source” or similar (some drivers have this)
Event Viewer → Windows Logs → System → look for events with source “e1dexpress” / “Netwtw” / “rt640x64” containing “Wake” or “Magic Packet”

Linux:

# Show WoL status
ethtool eth0 | grep -i wake

# Enable magic packet logging (kernel must support it)
echo 1 > /sys/class/net/eth0/device/power/wol_reason_log  # not available on all drivers

# Or just monitor dmesg after sending packet while awake
dmesg -w | grep -i "magic\|wol\|wake"

4. Simplest test loop (recommended practical method)

Boot the computer normally
From another machine send WoL packets every 10–15 seconds (your python script is fine)
On target PC run Wireshark or tcpdump with filter shown above
Confirm the packet arrives → then you know the network path is correct
Shut down / sleep the PC
Send again → if it wakes → everything works end-to-end

Summary – Quick decision tree

Goal	Recommended method	Reliability
Prove packet reaches NIC	Wireshark / tcpdump capture	★★★★★
Quick visual check	Watch Ethernet LED blink	★★★☆☆
Confirm OS sees wake reason	Event Viewer / dmesg	★★★★☆
Full end-to-end test	Capture while on → then sleep → wake	★★★★★

Most people find step 1 (packet capture while PC is on) the fastest way to answer:
“Is the magic packet even reaching the computer?”

References:

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