ICQ Legacy Client Setup (ICQ 98a / 99a / 99b)

This guide explains how to install and configure ICQ 98a, ICQ 99a, or ICQ 99b for Open OSCAR Server using the legacy ICQ protocol (v3-v5 over UDP).

These clients use the legacy ICQ protocol, which is different from the OSCAR protocol used by ICQ 2000b and later. The server must have legacy ICQ support enabled (ICQ_LEGACY_ENABLED=true, which is the default). The protocol version is auto-detected from each client's packets.

Protocol Versions

Version	Clients	Status
V5	ICQ 99a, ICQ 99b	Supported (default)
V4	ICQ 98a (some builds; later builds use V5)	Supported (default)
V3	ICQ Groupware	Supported (default)
V2	ICQ 1.111 Beta (1997, Win95/NT4 only), ICQ 1.111 Beta for Windows 3.11, open-source center client (early centericq/centerim)	Supported (default)
V1	ICQ 1.02 Beta (1996)	Unsupported (logging only)

V1 clients (ICQ 1.02 Beta) require Windows 95 or NT 4.0 and will not install on later versions. V2 clients (ICQ 1.111 Beta, 1997) also require Windows 95/NT4 or Windows 3.11. The V2 protocol supports login, messaging, authorization, presence, status changes, contact list, search, and profile updates. V2 clients see advanced statuses (N/A, Occupied, DND) from later clients mapped to the closest V2 equivalent (Away or DND).

Download

Download ICQ 98a, 99a, or 99b from oldversion.com or another software archive site. Third-party clients that use the legacy ICQ protocol (V3-V5) should also be supported -- feel free to test and report.

Installation

Windows

Run Installer

Run the ICQ installer and follow the prompts.

Start Registration Wizard

After installation, the ICQ registration wizard will appear.

Configure Server

Click the For admin use button at the bottom of the registration wizard.

Enter the following:

Server: Your server's hostname or IP address (e.g. 127.0.0.1 for local testing, or your server's public IP/hostname).
Port: 4000 (the default legacy ICQ UDP port).

Click OK to save the server settings.

Complete Registration

Proceed through the registration wizard as normal. You can either register a new account or log in with an existing one, depending on your server configuration.

If ICQ_LEGACY_AUTO_REGISTRATION=true is set in your server config, the client can create new accounts directly through the registration wizard. Otherwise, create accounts via the management API first.

Linux

You can run ICQ 98/99 under Linux via WINE.

Install WINE

Install WINE for your distribution.

Run the Installer
```
wine icq99a.exe
```
Configure Server

When the registration wizard appears, click For admin use and enter your server hostname and port 4000 as described in the Windows steps above.

Complete Registration

Proceed through the wizard as normal.

Server Configuration

The legacy ICQ server listens on UDP port 4000 by default. Key settings in config/settings.env:

# Enable legacy ICQ protocol support
ICQ_LEGACY_ENABLED=true

# UDP listener address
ICQ_LEGACY_UDP_LISTENER=0.0.0.0:4000

# Supported protocol versions (V2, V3, V4, V5 are production-ready)
ICQ_LEGACY_VERSIONS=2,3,4,5

# Enable direct connections for following protocol versions for peer-to-peer
# communication (file transfer, direct chat). Will leak client IP address
# in presence notifications. Mixing direct connections between different ICQ
# versions can cause older clients to crash on peer-to-peer connection requests.
ICQ_LEGACY_DIRECT_CONNECTIONS=5

Docker

If running via Docker, ensure UDP port 4000 is mapped in docker-compose.yaml:

ports:
  - "4000:4000/udp"

This mapping is included in the default docker-compose.yaml.

Troubleshooting

Client connects but nothing happens: Verify the server shows legacy ICQ server started in the logs with the correct port and versions.
Connection timeout: Check that UDP port 4000 is reachable from the client. Firewalls often block UDP traffic by default.
Registration fails: Ensure ICQ_LEGACY_AUTO_REGISTRATION=true is set, or create the account via the management API before logging in.
File transfer / direct chat not working: Enable direct connections for the client's protocol version: ICQ_LEGACY_DIRECT_CONNECTIONS=5 (or 3,4,5).

CLIENT_ICQ_LEGACY.md 4.5 KB 文件历史 原始文件