Multiplayer Guide

Version Compatibility Strategy

jrpm is a tagged version (jrpm-0.1.0), requiring the revision string to match exactly for multiplayer handshake:

Scenario	Behavior
jrpm client ↔ jrpm server	✅ Normal connection (version matches)
jrpm client ↔ original jgrpp / pulsexlb server	❌ Rejected (version isolation)
Original jgrpp client → jrpm server	✅ Allowed (server-side relaxes acceptance of jgrpp-* revision)
pulsexlb client → jrpm server	✅ Allowed (accepts pxp revision)

NewGRF Version

Regardless of the client's version, NewGRF version must exactly match the server (_openttd_newgrf_version is strictly validated) — this is the baseline for deterministic simulation.

Setting Up a Server

# Dedicated server (no GUI)
openttd-jrpm -D -c server.cfg

Recommended server.cfg configuration (see Server Performance Tuning for details):

[network]
server_name = My JRPM Server
server_port = 3979
max_clients = 32
max_companies = 15
frame_freq = 3
sync_freq = 50
commands_per_frame = 8
bytes_per_frame = 16
bytes_per_frame_burst = 512
max_join_time = 1000
max_download_time = 2000
max_lag_time = 1200

Joining a Server

• In-game: "Multiplayer → Join Internet Server/Add Server", or
• Command line: openttd-jrpm -n <host>:<port>

Content Download (NewGRF/Scenarios)

jrpm supports multi-mirror + parallel download:

[network]
content_server = content.openttd.org        ; metadata server
content_mirrors = https://binaries.openttd.org/bananas,https://your-mirror.example/bananas
content_download_parallel = 4               ; parallel download file count (1-8)

• Mirror list is comma-separated, used in order; failed mirrors automatically switch to the next;
• Environment variables OTTD_CONTENT_MIRROR_URI / OTTD_CONTENT_SERVER_CS take priority over settings;
• Falls back to the legacy TCP download protocol when all mirrors fail.

Server Administration

• Console commands: status, clients, kick, ban, save, reset_company, autogroup (vehicle auto-grouping), etc.;
• RCON: Set rcon_password on the server to send console commands remotely.