Mastering Server Communication with XServer: The Ultimate Bridge Plugin for Minecraft
Running a single Minecraft server is fun, but when you scale up to a network of servers—maybe a hub, multiple game modes, and a proxy—things get complicated fast. That is where XServer comes in. It is not a flashy minigame or a world generator; it is the silent workhorse that lets your plugins talk to each other across different servers. If you have ever tried to sync player data, send cross-server messages, or coordinate events between a Bukkit server and a BungeeCord proxy, you know the headache of managing raw sockets. XServer takes that pain away with a clean, developer-friendly API.
What Exactly Is XServer?
XServer is a helper plugin designed to close the communication gap between Minecraft servers. It allows you to send byte arrays from one server to another and receive them seamlessly. Think of it as a messaging bus that sits on top of TCP sockets, handling all the tricky parts—connection management, queuing, and even automatic reconnection. It works with both Bukkit (Spigot/Paper) and BungeeCord, and the core module can even be embedded in standalone Java applications. Originally built for massive server clusters, it has been battle-tested in environments with dozens of servers.
Why Server Communication Matters
Modern Minecraft networks rarely consist of a single world. You might have a lobby server, a survival world, a creative plot server, and a BungeeCord proxy routing players between them. Without a communication layer, each server is an island. XServer enables real-time data exchange, so a plugin on your lobby can query player stats from a survival server, or a minigame can notify the proxy to send a player back to the hub. This opens up possibilities like synchronized economies, global chat, and cross-server teleportation.
How XServer Works Under the Hood
XServer uses MySQL to manage server identities and passwords. Each server in your network gets a unique name, an address (host:port), and a shared password. When a connection is established, XServer handles duplex socket communication, meaning data can flow both ways without constantly reopening connections. Outgoing messages are automatically queued, and incoming messages are dispatched through a custom EventHandler, so your plugin code stays clean and event-driven.
Setting Up XServer
Getting started is straightforward, but you will need access to a MySQL database. First, create the required table with the following SQL (run it once on your database):
CREATE TABLE IF NOT EXISTS `xserver` (
`ID` int(11) NOT NULL AUTO_INCREMENT,
`NAME` varchar(64) COLLATE utf8_bin NOT NULL,
`ADRESS` varchar(128) COLLATE utf8_bin NOT NULL,
`PW` varchar(20) COLLATE utf8_bin NOT NULL,
PRIMARY KEY (`ID`),
UNIQUE KEY `ID` (`ID`),
UNIQUE KEY `ADRESS` (`ADRESS`),
KEY `ID_2` (`ID`)
) DEFAULT CHARSET=utf8 COLLATE=utf8_bin;Then insert a row for each server you want to connect. The NAME must be unique and identifies the server. ADRESS uses the format host:port (for example, localhost:19999). PW is the password that other servers will use to authenticate.
Bukkit Setup
Copy the XServer-Bukkit.jar into your plugin folder and start the server once. A configuration folder will be generated. Open config.yml and fill in your MySQL credentials and a servername. The key settings look like this:
- useMotdForServername: false (set to true if you want to use the server’s MOTD as its name)
- servername: theNameYouCalledThisServer
- mysql: User, Pass, Data, Host – your database connection details
BungeeCord Setup
The BungeeCord version follows the same pattern. Drop the JAR into the proxy’s plugin folder, run it once, and edit the generated config. The MySQL table is shared across all servers, so you only need to create it once.
For those who prefer a streamlined setup, you can manage plugins like XServer effortlessly using the foxygame.net launcher, a modern Minecraft launcher that lets you download mods and plugins right from its menu. This can save time when juggling multiple server instances and dependencies.
Commands and Administration
The Bukkit version of XServer includes a handy set of commands to monitor and control the network. All subcommands require the xserver permission. Here are the most useful ones:
- /xserver package [Servername] – Shows package speed to all servers, or a specific one.
- /xserver ping [Servername] – Pings all servers or a specific server.
- /xserver reconnect [s] – Reconnects all servers. Add the s flag for a soft reconnect (only those not currently connected).
- /xserver reload – Reloads the server list from MySQL and reconnects.
- /xserver status – Displays the current connection status for each server.
- /xserver stresstest [times=10] [targets=all] [async=false] – Runs a stress test. Targets can be all or a semicolon-separated list of server names.
These commands are invaluable for debugging network issues or simply verifying that your cluster is healthy.
Performance That Scales
XServer was built for serious server networks. In one real-world test, a network of 43 Bukkit servers and 2 BungeeCord proxies ran a stress test with a factor of 1000. That means 45,000 messages (each a 32-character string) were sent and returned, generating over 64 MBit/s of traffic on a single server. Despite the load, the average response time stayed between 80 and 90 milliseconds. This kind of performance is why large server clusters rely on XServer for near-real-time communication.
Developer API and Integration
If you are a plugin developer, XServer is a dream. You no longer need to write low-level socket code or worry about connection drops. The plugin provides an EventBus and a simple API to send messages. A companion open-source plugin, XComServerCommand, demonstrates how to use XServer in your own projects. The core module is separated from the Bukkit/BungeeCord code, so you can even embed XServer communication in a custom Java application that sits outside Minecraft entirely.
Where to Get XServer
The original author has stopped updating the plugin on BukkitDev. All future releases and snapshots are now on Spigot (resource ID: spigotmc.org/resources/xserver.270). You can also download the latest builds from the Maven repository at repo.rennschnitzel.de:8081/nexus/content/repositories/rs-public/de/mickare/xserver/. The source code is available on GitHub under the MIT license, so you can inspect, modify, and contribute.
Final Thoughts
XServer fills a niche that many server admins do not realize they need until they attempt to run a multi-server network. It abstracts away the complexity of socket programming, provides robust error handling, and scales impressively. Whether you are building a small BungeeCord setup or a massive server cluster, XServer is a reliable foundation for cross-server communication. Its shift to Spigot and the open-source model ensures that the plugin will continue to evolve, making it a smart choice for any network that demands seamless inter-server dialogue.