Troubleshoot in this order first

When friends can’t connect, there’s often more than one cause. Working through the list below, starting with the most common, saves the most time:

  1. Is the address and port correct? Have your friend verify that the address and port they entered match yours exactly. Java defaults to port 25565, Bedrock to 19132; if you changed the port when setting up the server, your friend must use the actual port you’re running on—don’t assume the default.
  2. Is the server actually online? Whether the server actually started, or whether it has crashed, isn’t something you can tell by eye. Use TopoBlocks’s free “monitor only”: enter the address and port and take a look—you’ll see the online status, version, player count, and latency.
  3. Do the versions match? The client and server must be on the same major version to connect, and Java and Bedrock are not interchangeable (a Java client can’t join a Bedrock server, and vice versa).
  4. Network and firewall. Whether the port is open to the outside, and whether your friend’s network can reach your address. The most common pitfall with home-network self-hosting is a port that isn’t forwarded or a public address that isn’t reachable.

Use the free monitor to quickly pinpoint which step

The key to troubleshooting is first distinguishing a “server problem” from a “problem on your friend’s end.” TopoBlocks’s “monitor only” is completely free and needs only the address and port:

  • The monitor shows online, with a version and latency → The server itself is fine, so turn your attention back to your friend’s end: whether the address and port are typed wrong, whether the versions match, whether their network is working.
  • The monitor also can’t connect → The problem is on the server side: it may be down, the address may be wrong, or the port may not be open.

It’s worth emphasizing that the monitor is read-only, has no write access at all, and never reads your world data—it only answers “can it connect, what version, how many players, what latency,” helping you narrow the problem down to a specific step. To learn how to correctly enter the address and connect on the client side, see Connecting to a Minecraft Server; if the monitor shows the server offline, see How to Troubleshoot a Server That Won’t Connect / Is Offline.

Version mismatch is a frequent cause

Many “can’t connect” cases are actually a version mismatch: the server is on one version, your friend’s client is on another, and the handshake fails. You can see the server’s version number directly in the monitor, so just have your friend switch their client to the matching version; for specifics, see What to Do When the Client and Server Versions Don’t Match. One more reminder: Java and Bedrock are two separate systems and are not interchangeable—first confirm that you and your friend are using the same one.

About capabilities “beyond monitoring”

The free monitor only looks; it doesn’t act. If you need to operate the server remotely—such as deploying a world, syncing resource packs, or applying security updates—those belong to the paid “full management” tier and will only run with your explicit authorization; pricing is shown in the app. When world files are involved, TopoBlocks’s red line is always to never overwrite the source files and to generate a traceable new version every time. To set up a server from scratch on your phone that friends can join, see How to Host a Minecraft Server From Your Phone.