Update Dockerfile

Dockerfile

@@ -28,6 +28,17 @@ RUN echo "eula=true" > eula.txt && \
 
 EXPOSE 25565
 
-# fire up tunnel then server
-CMD sh -c 'cloudflared tunnel --url tcp://localhost:25565 --no-autoupdate & \
-           exec java -Xmx2G -Xms2G -jar server.jar --nogui'
+# launcher script: start tunnel, wait for tcp url, print it, then run server
+RUN printf '%s\n' \
+    '#!/bin/sh' \
+    'set -e' \
+    'cloudflared tunnel --url tcp://localhost:25565 --no-autoupdate --logfile /tmp/cf.log &' \
+    'CF_PID=$!' \
+    'echo "waiting for cloudflared…"' \
+    'while ! grep -m1 "tcp://" /tmp/cf.log >/dev/null 2>&1; do sleep 1; done' \
+    'MC_URL=$(grep -m1 "tcp://" /tmp/cf.log | sed -n "s/.*\(tcp:\/\/[^ ]*\).*/\1/p")' \
+    'echo "minecraft public endpoint: $MC_URL"' \
+    'exec java -Xmx2G -Xms2G -jar /minecraft/server.jar --nogui' \
+    > /start.sh && chmod +x /start.sh
+
+CMD ["/start.sh"]