If during first time setup you have enabled the DSM 4.3 firewall on your Synology Diskstation then connecting Windows services (e.g. Data Replicator 3, Cloud Backup, Install Assistant, etc.) requires you to open those ports so that the two can communicate, this is why likely why you’ve run into the famous “Failed to connect to the target server. Check the network or server setting” error message when setting up Data Replicator 3. Here’s the fix:
- Connect to the Administration of your Synology Diskstation as an Administrator group user (e.g. admin)
- Open Control Panel > Firewall and QOS within the Network Services group
- Within the Allow / Deny tab ensure that the entry starting with “Synology Assistant, etc.” is enabled with Protocol set to All, Source IP set to All and Action Enabled
- Save changes
- Connect to your DiskStation via Data Replicator 3
That’s it!