Feature: Allow setting a different port in the motd (#4293)

* Allow changing the broadcasted port using a system property. This may be needed if the port Geyser runs on & the port Bedrock players connect on do not match - e.g. due to port forwarding/different routing.

* initial stab at making the broadcast port an (unsafe) config option

* Automatically set broadcast port to be the bind port unless manually overridden

* Warn about broadcast port mismatch

* Use 0 instead of -1 as indicator to broadcast the port geyser is running on

api/src/main/java/org/geysermc/geyser/api/network/BedrockListener.java

@@ -50,6 +50,14 @@ public interface BedrockListener {
      */
     int port();
 
+    /**
+     * Gets the broadcast port that's sent to Bedrock clients with the motd.
+     * This is the port that Bedrock clients will connect with. It usually does not differ from the listening port.
+     *
+     * @return the broadcast port
+     */
+    int broadcastPort();
+
     /**
      * Gets the primary MOTD shown to Bedrock players if a ping passthrough setting is not enabled.
      * <p>

core/src/main/java/org/geysermc/geyser/GeyserImpl.java

@@ -314,6 +314,22 @@ public class GeyserImpl implements GeyserApi {
                 }
             }
 
+            String broadcastPort = System.getProperty("geyserBroadcastPort", "");
+            if (!broadcastPort.isEmpty()) {
+                int parsedPort;
+                try {
+                    parsedPort = Integer.parseInt(broadcastPort);
+                    if (parsedPort < 1 || parsedPort > 65535) {
+                        throw new NumberFormatException("The broadcast port must be between 1 and 65535 inclusive!");
+                    }
+                } catch (NumberFormatException e) {
+                    logger.error(String.format("Invalid broadcast port: %s! Defaulting to configured port.", broadcastPort + " (" + e.getMessage() + ")"));
+                    parsedPort = config.getBedrock().port();
+                }
+                config.getBedrock().setBroadcastPort(parsedPort);
+                logger.info("Broadcast port set from system property: " + parsedPort);
+            }
+
             boolean floodgatePresent = bootstrap.testFloodgatePluginPresent();
             if (config.getRemote().authType() == AuthType.FLOODGATE && !floodgatePresent) {
                 logger.severe(GeyserLocale.getLocaleStringLog("geyser.bootstrap.floodgate.not_installed") + " "

core/src/main/java/org/geysermc/geyser/command/defaults/ConnectionTestCommand.java

@@ -31,6 +31,7 @@ import org.geysermc.geyser.GeyserImpl;
 import org.geysermc.geyser.api.util.PlatformType;
 import org.geysermc.geyser.command.GeyserCommand;
 import org.geysermc.geyser.command.GeyserCommandSource;
+import org.geysermc.geyser.configuration.GeyserConfiguration;
 import org.geysermc.geyser.session.GeyserSession;
 import org.geysermc.geyser.text.GeyserLocale;
 import org.geysermc.geyser.util.LoopbackUtil;
@@ -84,7 +85,7 @@ public class ConnectionTestCommand extends GeyserCommand {
                 return;
             }
         } else {
-            port = 19132;
+            port = geyser.getConfig().getBedrock().broadcastPort();
         }
         String ip = fullAddress[0];
 
@@ -112,30 +113,41 @@ public class ConnectionTestCommand extends GeyserCommand {
             return;
         }
 
-        // Issue: do the ports not line up?
+        GeyserConfiguration config = geyser.getConfig();
-        if (port != geyser.getConfig().getBedrock().port()) {
+
+        // Issue: do the ports not line up? We only check this if players don't override the broadcast port - if they do, they (hopefully) know what they're doing
+        if (config.getBedrock().broadcastPort() == config.getBedrock().port()) {
+            if (port != config.getBedrock().port()) {
                 if (fullAddress.length == 2) {
                     sender.sendMessage("The port you are testing with (" + port + ") is not the same as you set in your Geyser configuration ("
-                    + geyser.getConfig().getBedrock().port() + ")");
+                            + config.getBedrock().port() + ")");
                     sender.sendMessage("Re-run the command with the port in the config, or change the `bedrock` `port` in the config.");
-                if (geyser.getConfig().getBedrock().isCloneRemotePort()) {
+                    if (config.getBedrock().isCloneRemotePort()) {
                         sender.sendMessage("You have `clone-remote-port` enabled. This option ignores the `bedrock` `port` in the config, and uses the Java server port instead.");
                     }
                 } else {
                     sender.sendMessage("You did not specify the port to check (add it with \":<port>\"), " +
                             "and the default port 19132 does not match the port in your Geyser configuration ("
-                        + geyser.getConfig().getBedrock().port() + ")!");
+                            + config.getBedrock().port() + ")!");
                     sender.sendMessage("Re-run the command with that port, or change the port in the config under `bedrock` `port`.");
                 }
             }
+        } else {
+            if (config.getBedrock().broadcastPort() != port) {
+                sender.sendMessage("The port you are testing with (" + port + ") is not the same as the broadcast port set in your Geyser configuration ("
+                        + config.getBedrock().broadcastPort() + "). ");
+                sender.sendMessage("You ONLY need to change the broadcast port if clients connects with a port different from the port Geyser is running on.");
+                sender.sendMessage("Re-run the command with the port in the config, or change the `bedrock` `broadcast-port` in the config.");
+            }
+        }
 
         // Issue: is the `bedrock` `address` in the config different?
-        if (!geyser.getConfig().getBedrock().address().equals("0.0.0.0")) {
+        if (!config.getBedrock().address().equals("0.0.0.0")) {
             sender.sendMessage("The address specified in `bedrock` `address` is not \"0.0.0.0\" - this may cause issues unless this is deliberate and intentional.");
         }
 
         // Issue: did someone turn on enable-proxy-protocol, and they didn't mean it?
-        if (geyser.getConfig().getBedrock().isEnableProxyProtocol()) {
+        if (config.getBedrock().isEnableProxyProtocol()) {
             sender.sendMessage("You have the `enable-proxy-protocol` setting enabled. " +
                     "Unless you're deliberately using additional software that REQUIRES this setting, you may not need it enabled.");
         }
@@ -166,7 +178,7 @@ public class ConnectionTestCommand extends GeyserCommand {
                 String connectionTestMotd = "Geyser Connection Test " + randomStr;
                 CONNECTION_TEST_MOTD = connectionTestMotd;
 
-                sender.sendMessage("Testing server connection now. Please wait...");
+                sender.sendMessage("Testing server connection to " + ip + " with port: " + port + " now. Please wait...");
                 JsonNode output;
                 try {
                     String hostname = URLEncoder.encode(ip, StandardCharsets.UTF_8);

core/src/main/java/org/geysermc/geyser/configuration/GeyserConfiguration.java

@@ -122,6 +122,8 @@ public interface GeyserConfiguration {
 
         void setPort(int port);
 
+        void setBroadcastPort(int broadcastPort);
+
         boolean isCloneRemotePort();
 
         int getCompressionLevel();

core/src/main/java/org/geysermc/geyser/configuration/GeyserJacksonConfiguration.java

@@ -172,6 +172,15 @@ public abstract class GeyserJacksonConfiguration implements GeyserConfiguration
             return port;
         }
 
+        @Setter
+        @JsonProperty("broadcast-port")
+        private int broadcastPort = 0;
+
+        @Override
+        public int broadcastPort() {
+            return broadcastPort;
+        }
+
         @Getter
         @JsonProperty("clone-remote-port")
         private boolean cloneRemotePort = false;

core/src/main/java/org/geysermc/geyser/network/netty/GeyserServer.java

@@ -102,6 +102,11 @@ public final class GeyserServer {
 
     private ChannelFuture bootstrapFuture;
 
+    /**
+     * The port to broadcast in the pong. This can be different from the port the server is bound to, e.g. due to port forwarding.
+     */
+    private final int broadcastPort;
+
     public GeyserServer(GeyserImpl geyser, int threadCount) {
         this.geyser = geyser;
         this.group = TRANSPORT.eventLoopGroupFactory().apply(threadCount);
@@ -115,6 +120,13 @@ public final class GeyserServer {
         } else {
             this.proxiedAddresses = null;
         }
+
+        // It's set to 0 only if no system property or manual config value was set
+        if (geyser.getConfig().getBedrock().broadcastPort() == 0) {
+            geyser.getConfig().getBedrock().setBroadcastPort(geyser.getConfig().getBedrock().port());
+        }
+
+        this.broadcastPort = geyser.getConfig().getBedrock().broadcastPort();
     }
 
     public CompletableFuture<Void> bind(InetSocketAddress address) {
@@ -243,8 +255,8 @@ public final class GeyserServer {
                 .nintendoLimited(false)
                 .protocolVersion(GameProtocol.DEFAULT_BEDROCK_CODEC.getProtocolVersion())
                 .version(GameProtocol.DEFAULT_BEDROCK_CODEC.getMinecraftVersion()) // Required to not be empty as of 1.16.210.59. Can only contain . and numbers.
-                .ipv4Port(this.geyser.getConfig().getBedrock().port())
+                .ipv4Port(this.broadcastPort)
-                .ipv6Port(this.geyser.getConfig().getBedrock().port())
+                .ipv6Port(this.broadcastPort)
                 .serverId(bootstrapFuture.channel().config().getOption(RakChannelOption.RAK_GUID));
 
         if (config.isPassthroughMotd() && pingInfo != null && pingInfo.getDescription() != null) {

core/src/main/resources/config.yml

@@ -30,6 +30,9 @@ bedrock:
   # How much to compress network traffic to the Bedrock client. The higher the number, the more CPU usage used, but
   # the smaller the bandwidth used. Does not have any effect below -1 or above 9. Set to -1 to disable.
   compression-level: 6
+  # The port to broadcast to Bedrock clients with the MOTD that they should use to connect to the server.
+  # DO NOT uncomment and change this unless Geyser runs on a different internal port than the one that is used to connect.
+  # broadcast-port: 19132
   # Whether to enable PROXY protocol or not for clients. You DO NOT WANT this feature unless you run UDP reverse proxy
   # in front of your Geyser instance.
   enable-proxy-protocol: false