Since BDS 1.26.50, NetherNet is the default transport — and plenty of server owners run into a server that simply won't accept connections. This guide walks through the settings and port forwarding a NetherNet server needs, and how to narrow down what is wrong.
server.properties needs these three settings:
transport=nethernet (optional — it is the default)server-udp-ports=[ip:]external[-external]:internal[-internal]server-udp-ports=203.0.113.1:49132-49151:19132-19151server-udp-ports=[2001:db8::1]:49132-49151:19132-19151server-port=19132transport selects the transport. As of 1.26.51 you can choose nethernet or raknet.
server-udp-ports sets the server IP and UDP ports as the player sees them, plus the ports the origin server (the actual BDS host behind NAT/forwarding) binds to.
As of 1.26.51 the external and internal port ranges must be the same length, and you need at least as many ports as players who log in. Example: for a server with 20 players you must open 20 ports, e.g. server-udp-ports=203.0.113.1:49132-49151:19132-19151.
server-port=19132 selects the TCP port used for the WebRTC signaling described below.
The rest of this guide assumes:server-udp-ports=203.0.113.1:49132-49151:19132-19151server-port=19132
The ports the origin server must open:
19132/tcp # the port set in server-port
19132-19151/udp # the internal ports set in server-udp-ports
And the ports that must be open to the outside (forwarded to the origin):
19132/tcp --> origin:19132/tcp
49132-49151/udp --> origin:19132-19151/udp
Mind the UDP ports. The client is handed one of 49132-49151 (learned from its query to 19132/tcp), so the external UDP ports you open are decided by server-udp-ports. The internal routing must map one-to-one: 49132 → 19132, 49133 → 19133, and so on.
Also, 19132/tcp is the signaling port for the WebRTC offer exchange. HTTP traffic arrives there, so proxy it (for example with nginx) or add HTTPS if you need to — setting up a NetherNet Bedrock server on Debian/Ubuntu may help.
Once BDS starts, it should already be reachable. From an external network (for example a 4G/5G line), connect with:
Address: 203.0.113.1 (the server's global IP)
Port: 19132
To use a different port, change the outward TCP port from step 1. If you want HTTPS or virtual hosting with nginx, see how to set up a NetherNet-ready Bedrock server on Debian/Ubuntu.
If the connection fails, check the following:
Use this site's tool to check whether the TCP connection works — mind the 2-minute cache.
Re-check your port settings — especially the one-to-one UDP port mapping.
It may be an issue with your internet provider, which is out of scope for this article.
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