On startup, YAPI locates YAPI Service by listening on UDP network port 18002.

In event when YAPI is unable to locate Service the following message will popup.


The issue can be resolved by working through the following troubleshooting steps.

Note that If only few workstations exhibit the problem go directly to step 3.

1. Check whether YAPI Service is running.

2. Check whether the server that runs YAPI Service has firewall open for YAPI network traffic. More on YAPI network ports here.

3. Check whether this computer is connected to your office local area network and is on the same subnet as the server that runs YAPI Service. More on network subnets here.

4. Check if Windows Firewall prevents YAPI listen for YAPI Service advertizing on port 18002. More on YAPI network ports here.

Normally, YAPI clears firewall first time it runs: if your computer has Windows Firewall enabled, you will see the following Windows Security Alert. You should click Allow access to let YAPI communicate with YAPI Service via the network.


If you accidentally clicked Cancel YAPI won’t be able to communicate with YAPI Service and you will see error E041.

Unfortunately, when you start YAPI next time, you won’t see Windows Security Alert anymore — just YAPI E041 error message. Now you will need to setup Windows Firewall manually to enable YAPI communicate on the network.

Click here to find out how to configure Windows Firewall. The recommended solution is to delete YAPI record in Windows Firewall rules so next time you start YAPI you will see Windows Security Alert again.

Here is how you delete YAPI record in Windows Firewall configuration on  Windows 7: open Control Panel, click System and Security, Click Windows Firewall, click Advanced Settings on the left. When the Advanced Settings screen appear, select Inbound Rules from the left. Select yapiruntime.exe on the right. Press Del key on the keyboard. Click Yes to confirm deletion.

5. Check whether Antivirus software, Personal Firewall software, or any other security features on your computer prevent YAPI to communicate with YAPI Service. More here.

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