When a firewall or network blocks your game port

If one player times out while everyone else is in, something between that player and your server is dropping the traffic. This shows you where blocking happens, how to test it in a minute, and which networks genuinely cannot be worked around.

6 min read · Updated Oct 21, 2026 · By GuavaHost Team

First, the part that is not the problem. Your GuavaHost server's ports are open to the internet from the moment the server starts. There is no router in front of it for you to configure, and no port forwarding to do. So if some players are in and one is not, the blocking is happening on that player's side, somewhere between their game and the internet.

What blocking looks like

A blocked port almost always produces a timeout, not a refusal. The game sits on a connecting screen for ten or twenty seconds and then gives up. There is no helpful message, because nothing answered at all: the packets were silently discarded.

That matters, because it tells you what you are not looking at:

• A timeout means nothing answered. Blocked port, wrong address, or a server that is not running.
• A refusal means something answered and said no. A password, a whitelist, a ban, or a full server.
• A message about versions, sessions or authentication is a different problem entirely, and the full connection checklist sorts those out.

So before blaming a firewall, confirm the server status reads Online in the panel and that the player is using the exact address from next to Address on the server page, port included.

The one minute test

Have the affected player try the server from a completely different network. The easiest version: turn off Wi-Fi on their phone, start a mobile hotspot, connect the PC to that and try again. On a phone or tablet game, just switching off Wi-Fi is enough.

• Works on mobile data, fails at home. Their home network or their own machine is blocking it. Keep reading.
• Fails on both. It is not their local network. Go back to the address, the version and the server's status.
• Works at a friend's house, fails at home. Same conclusion as the first case.

One thing to know before you reach for an online port checker: those tools test TCP only. Most game traffic is UDP, which has no handshake, so a checker cannot tell you whether a UDP port is reachable. A real join attempt is the only honest test. TCP versus UDP ports explains which games use which.

Once the test points at the player's side, there are six places worth checking, in roughly the order they turn out to be the culprit.

The player's own firewall or antivirus

Windows asks for permission the first time a game wants network access, and it is easy to dismiss the prompt. Third party security suites are worse: they add their own firewall and their own network protection on top, and they block quietly.

To test it, have the player turn off the suite's firewall or network shield for one attempt, then turn it straight back on. If that was it, add an exception for the game rather than leaving protection off. On Windows, you allow the game through Defender Firewall by allowing the app, not by opening a port, because the player is connecting out rather than hosting anything.

Their router

Home routers rarely block outbound game traffic, but a few things on them do:

• A parental controls or safe browsing profile applied to that device, often set up and forgotten.
• A gaming or QoS mode throttling instead of helping.
• An older router running out of connection slots when the household is busy, which shows up as joins that work only sometimes.

Rebooting the router clears the last one. The other two are in the router's settings page.

A school, office, student halls or hotel network

This is the most common hard case. Managed networks allow the ports that do normal work, typically web traffic on 80 and 443, and drop everything else. Game ports are exactly the sort of thing they are built to drop. Captive portal networks, the kind where you accept terms on a web page first, are also usually filtering well beyond that page.

There is no setting the player can change, and no trick on your side that fixes it. Your options:

• Have them play from a different network.
• If the network's owner is reachable and willing, they can allow the specific address and port. In practice, in a school or a hotel, they will not.

Moving your server's main port to 443 is a tempting idea, and we would not build a server around it: filtered networks often inspect the traffic rather than the port number, and you would be changing everyone else's address for one player. If you want a different port for other reasons, add and manage your server's ports shows how.

A VPN

VPNs cause this in both directions. A VPN that is on can route game traffic through a server that blocks or mangles it, and some free VPNs break UDP altogether. Equally, a player on a filtered network sometimes needs a VPN to get out at all.

The test is to toggle it: try once with the VPN off, once with it on. Whichever works, that is the answer for that player. If a VPN is required, pick an exit location near your server's region, because the extra hop adds ping on top of the real distance.

Mobile data and carrier grade NAT

Joining a server on mobile data usually works fine, because the player is making an outbound connection. What mobile connections cannot do is host, because the carrier shares one public address between many customers (carrier grade NAT), so incoming connections cannot be routed to a specific phone. Addresses from 100.64.x.x to 100.127.x.x are the giveaway.

So a player on mobile data can join, but their ping is higher and less steady, and a join that drops on a train is the network, not your server.

IPv6 only connections

A few home connections, and more mobile ones, hand out only an IPv6 address and reach IPv4 addresses through a translation layer. Most games cope, some do not, and the failure looks like a timeout. If a player on a modern fibre line cannot reach anything while mobile data works, this is worth asking their provider about.

What to tell a blocked player

Keep it short and in this order:

1. Fully close the game and relaunch it, then paste the address fresh rather than editing the saved entry.
2. Turn off any VPN and try again.
3. Allow the game through your firewall, or pause a third party security suite for one attempt.
4. Try from a phone hotspot. If that works, the problem is your home network.
5. If you are on a school, work or hotel network, play from somewhere else. That network is dropping game traffic by design.

Common questions

Do I need to open ports on my GuavaHost server?

No. Your server's ports are already reachable from the internet while it is running, and there is no firewall of yours in front of it. Any blocking is on a player's side.

Why can one player join and another cannot on the same address?

Because the address is only half of it. The other half is the path between each player and the server, and that path runs through different firewalls, routers and networks for each of them.

Will changing my server's port get around a school or office block?

Usually not. Managed networks often inspect the traffic itself rather than trusting the port number, and moving your port changes the address for everyone else too. Playing from a different network is the reliable answer.

Can a VPN fix a blocked game port?

Sometimes. A VPN can carry game traffic out of a restrictive network, and it can equally be the thing breaking it, so test with it both on and off. If you keep it on, choose an exit near your server's region to limit the extra ping.

Still stuck? Jump into our Discord at discord.gg/GuavaHost and the team will help you out.

• connecting
• firewall
• networking
• troubleshooting
• vpn

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