Low ID

What is a Low ID?

eMule Qt talks to other peers over two listen ports, one TCP and one UDP. When other peers on the internet cannot reach those ports, they cannot connect to you. You can still connect out to them, but nobody can connect in.

The networks notice this. An eD2K server gives you a Low ID instead of a High ID, and Kad reports you as Firewalled.

.:Quick check

Look at the status bar at the bottom of the main window. It shows your eD2K and Kad state. Green means all is well: eD2K: Connected and Kad: Connected. Orange means you are reachable only one way: eD2K: Connected (LowID) or Kad: Connected (Firewalled). If either one is orange, read on.

What it costs you

Low ID to Low ID does not work over plain eD2K. Two Low ID clients cannot exchange data with each other, because neither one can accept the other’s connection.
Fewer sources, slower downloads. Every other Low ID client that has your file is out of reach. On a busy network that is a large share of the sources.
You help the network less. Fewer peers can download from you, and your upload credits grow more slowly.

eMule Qt softens this. Its NAT traversal can still connect some pairs of Low ID clients. It cannot connect all of them, though, so a High ID is always better.

1. Let eMule Qt open the ports: UPnP and NAT-PMP

Most home routers can open ports on request. eMule Qt asks for this automatically with UPnP, NAT-PMP and PCP.

In eMule Qt, open Options → Connection and make sure Use UPnP to Setup Ports is ticked. It is on by default. The line next to it shows whether the forwarding really worked.
On your router, open its web page (often http://192.168.0.1 or http://192.168.1.1) and turn on UPnP or NAT-PMP. Some routers ship with it switched off.
Restart eMule Qt and reconnect.

The Automatic Port Mapping page explains how this works in detail.

2. Forward the ports on your router

If UPnP is not available, or does not work, open the ports by hand.

Find your ports in Options → Connection. eMule Qt picks a random TCP and UDP port the first time it starts, so yours are unique to you. You can change them there.
Find your computer’s local IP address, for example 192.168.1.23. It is in your operating system’s network settings, or in the router’s list of connected devices.
In the router, look for Port forwarding, Virtual server or NAT. Add one rule for the TCP port and one for the UDP port, both pointing to your computer’s local IP.
Give your computer a fixed local IP (often called DHCP reservation), so the rules still point to it after a restart.

3. Allow eMule Qt through your firewall

Even with an open router, the firewall on your computer can still block incoming connections. The program that listens is the core, emulecored.

Windows: when Windows asks whether eMule Qt and emulecored may communicate, allow them on private and public networks. Or add rules for your ports in an administrator command prompt (replace the numbers with yours):
netsh advfirewall firewall add rule name="eMule Qt TCP" dir=in action=allow protocol=TCP localport=4662
netsh advfirewall firewall add rule name="eMule Qt UDP" dir=in action=allow protocol=UDP localport=4672
macOS: if the firewall is on, open System Settings → Network → Firewall → Options and set eMule Qt and emulecored to Allow incoming connections.
Linux: with ufw, run (again with your own ports):
sudo ufw allow 4662/tcp
sudo ufw allow 4672/udp

4. Test your ports

Check that the outside world can reach you. In Options → Connection, click Test Ports. It opens our Test Ports page with your ports filled in, which tries to connect to them from the internet and tells you which ones are open.

If both ports pass, reconnect to the server. You should now get a High ID and a green status bar.

5. Still Low ID? You may be behind CGNAT

Some internet providers put many customers behind one shared public address. This is called carrier-grade NAT (CGNAT). Port forwarding cannot work there, because the blocking router belongs to your provider, not to you.

To check, compare two addresses:

The WAN or internet IP shown on your router’s status page.
The IP that a website such as a “what is my IP” page shows you.

If they differ, and the router’s WAN IP starts with 100.64 to 100.127 (the range 100.64.0.0/10), or with 10., 192.168. or 172.16 to 172.31, then you are behind CGNAT.

What you can do:

Ask your provider for a public IPv4 address. Many will switch you on request. Some charge a small fee.
Use a VPN that offers port forwarding. Forward the port the VPN gives you, and set the same number as your port in Options → Connection.
Use IPv6. CGNAT usually only affects IPv4. When both you and the other peer have IPv6, you can connect directly. See IPv6 Everywhere.

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