The 4Dpeer.txt file (text file) contains a UUID. This is used when logging on to the server for client identification in v17.

For example: Client connects via LAN. Goes into sleep mode (fold down notebook lid). User changes in meeting room and uses WLAN, thus receives new IP address. Client wakes up again, but is not accepted for reactivating the session because of a different IP address. In order to be able to delete it (otherwise locked records, open transaction, 4D license, etc), this UUID serves as identification, old client session is deleted, new one is started.

If this file exists on a machine and the machine is cloned, thus creating a situation where multiple clients have the same UUID, an issue will arise when subsequent machines attempt to login using the same UUID. In this situation, the 4Dpeer.txt file can be deleted so that it is recreated with a new UUID upon the next launch of 4D.

The 4Dpeer.txt file is located here:
Windows: %APPDATA%\4D\4DPeer.txt (C:\Users\UserName\AppData\Roaming\4D\4DPeer.txt)
macOS: ~/Library/Application Support/4D/4DPeer.txt (/Users/Username/Library/Application Support/4D/4DPeer.txt)