Self-hosting · Protocols
Open OSCAR Server Setup Checker & Config Generator
Pick your AIM or ICQ client and your host machine. This page tells you whether Open OSCAR Server supports it, which port that client must reach, which features work, and gives you the settings.env block, firewall rules and first-user command — plus, for Sri Lankan hosts, a CGNAT verdict and the CEB running cost.
By Induwara AshinsanaUpdated Sep 23, 2026
How it works
Open OSCAR Server does not speak one protocol. It speaks four, and a client that arrives on the wrong one gets a connection refused rather than a useful error. The checker resolves that in five steps, all read from the project's own files at commit 7bdd674.
- Client to dialect.The README's supported-client list maps each family to a dialect. AIM v1.x–v7.x, Pidgin and ICQ 2000b onward speak OSCAR; TiK, gaim and Quick Buddy speak TOC 1.0; vAIM, Miranda ~0.4.0.3 and iEM 1.0.1 speak TOC 2.0. ICQ 98a, 99a and 99b predate OSCAR and use the Mirabilis UDP protocol. AIM 6.2–7.5 are a fifth case: OSCAR wrapped in TLS, with Kerberos authentication.
- Dialect to port. From
config/settings.env: OSCAR listens on TCP 5190 viaOSCAR_LISTENERS, TOC on TCP 9898 viaTOC_LISTENERS, legacy ICQ on UDP 4000 viaICQ_LEGACY_UDP_LISTENER— and only whenICQ_LEGACY_ENABLED=trueand the client's protocol version appears inICQ_LEGACY_VERSIONS(valid values 1 to 5, with 1 experimental). AIM 6.2–7.5 use 443 instead — a separate TLS setup this generator deliberately does not fake. - Feature matrix.Two README rules are not uniform and have to be encoded rather than assumed. Buddy icons carry the qualifier “(v4.x, v5.x)”, so they are a no for v1.x–v3.x and are not claimed for v6.x/v7.x. File sharing splits three ways: Direct Connect and Get File are LAN only, while Send File works over the internet once the sending client forwards its own transfer port. Where the project does not claim a feature for a family, the table says “not listed” rather than guessing.
- Listener strings.
OSCAR_LISTENERSis a bind address;OSCAR_ADVERTISED_LISTENERS_PLAINis what the server publishes to clients. Behind NAT they differ, and that is where most first attempts fail. The generator emits127.0.0.1for a same-machine setup, the LAN address for a LAN setup, and for a port-forwarded setup the documented dual form —WAN://host:5190,LAN://ip:5191— since names and ports must both be unique and every advertised listener needs a matching bind listener. It also flipsDISABLE_AUTHto false once anything but the host can reach the port: left on, it creates an account for any name that signs in. - Reachability and running cost. A port forward only works if the address on your router is the address the internet sees, so rather than assert what any named operator does, the tool gives a common default plus the self-check that settles it. The cost panel computes energy as
watts × 24 × 30.44 ÷ 1000kWh per month, then prices it marginally: the difference between your household's bill with and without the server. Sri Lanka's domestic tariff is retroactive, so crossing a slab boundary reprices every unit already consumed and multiplying kWh by the sticker rate understates the real cost, sometimes threefold. Rates come from the site's verified tariff module (PUCSL — Decision on Electricity Tariffs, May 2026), and the figure is cross-checked against a second, independently written formula.
Everything runs in your browser: nothing you type is sent anywhere, and the compatibility matrix is a dated snapshot rather than a live query, so the recorded commit tells you exactly what it was read from.
Worked examples
Port quick reference
Every listener Open OSCAR Server opens, and who has to reach it. Defaults from config/settings.env.
| Port | Protocol | Variable | Used by |
|---|---|---|---|
| 5190 | TCP | OSCAR_LISTENERS | AIM v1.x–v7.x, Pidgin, ICQ 2000b and later |
| 9898 | TCP | TOC_LISTENERS | TiK, gaim, Quick Buddy, vAIM, Miranda, iEM |
| 4000 | UDP | ICQ_LEGACY_UDP_LISTENER | ICQ 98a, 99a, 99b and other pre-OSCAR clients |
| 8080 | TCP | API_LISTENER | You, on the host only — creates and deletes accounts |
| 8081 | TCP | WEBAPI_LISTENERS | Browser-based clients calling the web API |
| 443 | TCP | (separate TLS setup) | AIM 6.2–7.5, Kerberos over TLS |
Source: config/settings.env and docs/TOC.md at commit 7bdd674. Verified 2026-09-23.
Frequently asked questions
Open OSCAR Server is an MIT-licensed chat server written in Go that reimplements OSCAR, the protocol behind AOL Instant Messenger and ICQ. Vintage Windows AIM and ICQ clients connect to it and work. It is an independent project, not affiliated with AOL, and it ships a SQLite database and an HTTP management API for administering users and chat rooms.
Windows AIM v1.x through v7.x, TOC 1.0 clients (TiK, gaim, Quick Buddy), TOC 2.0 clients (vAIM, Miranda ~0.4.0.3, iEM 1.0.1), and Windows ICQ from the 1996 Mirabilis betas through 98x, 99x, 2000x, 2001x, 2002x, 2003x, 4 and 5. Pidgin connects too. The checker above lists the exact dialect and feature set for each family.
Four. TCP 5190 for OSCAR (AIM and ICQ 2000b onward), TCP 9898 for TOC 1.0 and 2.0, UDP 4000 for the pre-OSCAR ICQ protocol, and TCP 8080 for the management API — which binds to 127.0.0.1 by default and should stay there. The web API defaults to TCP 8081.
Because TOC is a different protocol from OSCAR and has its own listener. TiK, gaim and Quick Buddy speak TOC 1.0; vAIM, Miranda and iEM speak TOC 2.0. Both go to TOC_LISTENERS on port 9898, not to OSCAR_LISTENERS on 5190. The TiK setup guide still names the older TOC_HOST and TOC_PORT variables; the current one is TOC_LISTENERS, taking host:port pairs.
OSCAR_LISTENERS is what the server process binds — almost always 0.0.0.0 on a port. OSCAR_ADVERTISED_LISTENERS_PLAIN is the hostname the server hands back to clients so they know where to reconnect for other services. Behind NAT the two are different values, and setting the advertised one to 0.0.0.0 or to a private IP that external clients cannot resolve is the usual reason a login succeeds and then stalls.
Through the management API on the host itself. On Linux or macOS: curl -d '{"screen_name":"first-user", "password":"..."}' http://localhost:8080/user. On Windows use Invoke-WebRequest from PowerShell, not Command Prompt. For ICQ the screen name is a numeric UIN. The shipped config sets DISABLE_AUTH=true, which auto-creates accounts at login — fine on loopback, reckless on a network anyone else can reach.
On a LAN, yes, with nothing to configure at the router. Over the internet it depends on whether your connection has a forwardable public address. Mobile-broadband routers almost never do. Compare your router's WAN IP with what an external "what is my IP" page reports: if they differ, or the router shows 100.64.x.x – 100.127.x.x, a port forward cannot reach you and you need a static-IP add-on, an outbound tunnel, or a small VPS relay.
Partly. Direct Connect and Get File are documented as LAN only. Send File works across the internet, but the sending client must set a high file-transfer port in its AIM preferences and forward that TCP port to its own machine at the router. Rendezvous also reveals the sender's IP address to the recipient, which is worth knowing before you enable it.
AIM v4.x and v5.x only. The project lists buddy icons with that version qualifier, so v1.x–v3.x do not have them and the feature is not claimed for v6.x/v7.x. TOC clients do not get them either — the Buddy Art structure is documented as not fully understood. If buddy icons matter to your setup, AIM 5.x is the client to install.
About 5.1 kWh a month at 7 W (7 × 24 × 30.44 ÷ 1000). The rupee figure depends entirely on your household's existing consumption, because the CEB domestic tariff reprices every unit when you cross a slab boundary. At 90 units a month those 5 kWh cost roughly Rs 580, not the Rs 184 the headline rate suggests. The calculator above does the real arithmetic.
Yes. AIM 6.0–6.1 need their authentication mode switched to BUCP by editing serviceManifest.xml, because there is no UI for server settings. AIM 6.2–7.5 authenticate with Kerberos over TLS on port 443, and need the server's certificate database copied into %APPDATA%\acccore\nss on the client, with the Host field matching the certificate's Common Name. This page generates the plain listener block, not the TLS one.
No. OSCAR is a protocol from the 1990s and reimplementing it accurately does not give it modern security properties. Run it as a protocol lab you control, or as internal chat on a closed network — a computer lab, a hostel, a hackathon venue, an office with no internet dependency. Anything you would not want read should go somewhere else.
Sources & references
- Open OSCAR Server — project repository (MIT)
- README.md — supported clients and the AIM / ICQ feature matrix
- config/settings.env — every listener variable and its default port
- docs/CLIENT_ICQ.md — legacy UDP versus OSCAR by ICQ era
- docs/AIM_6_7.md — AIM 6.x/7.x, BUCP and the TLS path on port 443
- docs/RENDEZVOUS.md — file transfer over the internet
- docs/TOC.md — TOC 1.0 / 2.0 specification and the default port
- PUCSL — Retail Tariff Determination (effective 16 March 2025)
- Ceylon Electricity Board — tariff information
The compatibility matrix, ports and environment variables on this page were read from the project's own files at commit 7bdd674 on 2026-09-23. The project is under active development, so re-check against the repository if that commit is no longer on the default branch. Electricity rates are imported from this site's verified tariff module rather than re-entered, so a tariff revision updates every page at once.
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Comments & feedback
Spotted a bug or want an improvement? Tell us — our team reviews every comment, and good ideas get built. Comments are public and anonymous.
Found a client that behaves differently, or an upstream change this page has missed?
Email me at [email protected] — most fixes ship within 24 hours.