High ID and Low ID
In the eD2k network, every client is assigned a numeric ID by the server it connects to. This ID determines whether the client can accept incoming connections from other peers. The distinction between High ID and Low ID is one of the most fundamental concepts in the eD2k network, and it has a direct impact on download performance and which other clients you can exchange data with.
This page describes the eD2k protocol concept. For the practical steps to actually obtain a High ID — port numbers, firewall and router configuration, testing and troubleshooting — see Network Connectivity in the User Manual. The equivalent connectivity status on the Kademlia network is open / firewalled, described in Kademlia Network.
What is a Client ID?
When a client successfully connects to an eD2k server, the server assigns it a unique numeric ID for that session. This ID:
- Identifies the client to that specific server only — it is not global across all servers.
- Is reassigned every time the client reconnects to a server.
- Determines whether the client is reachable by other peers without server assistance.
Two categories of ID exist: High ID and Low ID.
High ID
A client receives a High ID when its Standard Client TCP port (default: 4662) is reachable from the internet — that is, no NAT router or firewall is blocking incoming connections to that port.
Value
The High ID is not an arbitrary number: it is derived directly from the client's public IP address using the following formula:
High ID = A + 256·B + 256²·C + 256³·D
where the client's IP address is A.B.C.D
For example, IP 80.12.34.56 produces:
80 + (12 × 256) + (34 × 65,536) + (56 × 16,777,216) = 939,851,344
Any ID value at or above 16,777,216 (16 million) is a High ID.
Benefits
- Full peer-to-peer connectivity. Clients with High ID can accept incoming connections from any other client — both High ID and Low ID.
- Direct transfers. Two High ID clients connect directly to each other without server involvement.
- No server restrictions. Many large eD2k servers refuse connections from Low ID clients to reduce their own relay load; having a High ID avoids this.
- Full source availability. A High ID client sees all sources (both High ID and Low ID) as "available sources" for download.
Low ID
A client receives a Low ID when its Standard Client TCP port is blocked by a NAT router or firewall, so that other clients cannot initiate connections to it. Any ID value below 16,777,216 (16 million) is a Low ID.
Low IDs are typically small numbers assigned incrementally by the server — they carry no information about the client's IP address.
Consequences
- Cannot accept direct incoming connections. The server must relay connection setup on behalf of the Low ID client.
- Two Low ID clients cannot transfer data to each other. A direct connection between two Low ID peers is impossible. Transferring data between them would require both to relay through the server simultaneously — a model eD2k servers do not support.
- Reduced available sources. For a Low ID client, only High ID peers count as "available sources". Low ID sources exist in the source list, but the Low ID client cannot initiate a connection to them.
- Server rejection. Many large servers reject Low ID clients outright to reduce relay overhead. This further limits which servers you can use.
- Lower effective download speed. Because only High ID peers can upload to a Low ID client (and the connection must be relayed through the server initially), download throughput is significantly reduced compared to High ID.
It is strongly recommended to obtain a High ID whenever possible. See Network Connectivity for how to do it.
The 16,777,216 threshold
The threshold 16,777,216 = 256³ is the smallest possible High ID value, corresponding to the IP 1.0.0.0. Any ID below this value cannot represent a real IP address and is therefore treated as a Low ID.
Summary
| Aspect | High ID | Low ID |
|---|---|---|
| ID value | ≥ 16,777,216 | < 16,777,216 |
| ID derivation | A + 256B + 256²C + 256³D (from public IP) | Small number assigned by server |
| Standard client TCP port | Reachable from internet | Blocked by NAT or firewall |
| Incoming connections | Accepted from any peer | Not possible; server relays |
| Transfer with another Low ID | Yes | No |
| Server acceptance | All servers | Many servers reject Low ID |
| Available download sources | All peers (High + Low ID) | High ID peers only |
Related Pages
- eD2k Network — network architecture, servers, file limits
- Network Connectivity — how to obtain a High ID (ports, firewall, router, troubleshooting)
- Kademlia Network — the serverless counterpart, with its own open / firewalled status
- Concepts & Glossary — all eD2k/Kademlia technical terms defined
- FAQ: Network & Connectivity — common questions about networks, ports and IDs