Plesk Migration fails: Panel Migrator failed to connect to RPC Agent

Symptoms

1. Migration fails with the following error:

   CONFIG_TEXT: Panel Migrator failed to connect to RPC Agent running on '203.0.113.2' server.
   RPC Agent is required for communication between current server and '203.0.113.2' server

   OR

   CONFIG_TEXT: Panel Migrator failed to start RPC Agent on '203.0.113.2' server. RPC Agent is required for communication between current server and '203.0.113.2' server First, check that Windows Administrator's credentials specified for the server are correct. If they are correct, it is very likely that File and Printer Sharing service is disabled on the remote server, so automatic start of agent is not possible. Try to upload RPC Agent installation package to the 203.0.113.2 server and run it manually.

   OR

   PLESK_ERROR: Failed to fetch basic information about resellers, clients and domains data from source servers 
   Cause: unpack requires a string argument of length 4 
   That is a critical error, migration was stopped. 

   OR

   CONFIG_TEXT: Error: Unable to start migration. Please check specified IP address, administrator login and password and try again. If issue still reproduced, refer logs to further investigation.

2. RPC Agent is installed and running on the source server.

3. On target host %plesk_dir%\\var\\modules\\panel-migrator\\sessions\\<sessiontimestamp>\\debug.log has the following data:

   CONFIG_TEXT: +|2015-11-02_08:25:24,017|D|MT|core.workflow.runner.by_subscription|||Checking whether it is required to execute action
   +|2015-11-02_08:25:24,017|D|MT|core.workflow.runner.by_subscription|||START: Get operation progress in current session
   +|2015-11-02_08:25:24,017|D|MT|core.workflow.runner.by_subscription|||FINISH: Get operation progress in current session
   +|2015-11-02_08:25:24,017|D|MT|core.workflow.runner.by_subscription|||Exit common action block

   info.log and debug.log files on the destination server have the following error:

   CONFIG_TEXT: URLError: <urlopen error [Errno 10054] An existing connection was forcibly closed by the remote host> PleskConnectionCheckError: Failed to connect to target Plesk server by Plesk API: <urlopen error [Errno 10054] An existing connection was forcibly closed by the remote host>

Cause

Network issue, required ports for migration are closed by a firewall.

Resolution

1. Follow the steps that migration tool suggests in the output:
   1. Check that there are no firewall rules blocking connections to 10155 port on 203.0.113.2 from that server.
      
      
   2. Make sure you could connect to the source server by 10155 port with "telnet" utility running on that server.

      C:\> telnet source_server_IP 10155

   3. Check that agent is running on the source server (panel-migrator-rpc-agent.exe process) and listening on 10155 port.
      If it does not, try to start 'panel-migrator-rpc-agent.exe', which is usually installed to %SYSTEMDRIVE%\\panel-migrator\\rpc-agent\\ .
      If it is still not running - investigate debug.log and info.log files on the target server
      (which are usually located at %plesk_dir%var\modules\panel-migrator\sessions\TIME_STAMP directory).
      
      
   4. Try to upload RPC Agent installation package to the 203.0.113.2 server and run it manually.
      The instructions on how to run RPC Agent manually can be found in the  article Migration cannot be started: Panel Migrator failed to install RPC Agent
2. Use Portqry utilities to ensure that all the ports listed below are accessible:

   CONFIG_TEXT: TCP ports 135, 139, 445 and UDP ports 137, 138. Be sure to open these ports on the source and on the target server.
   TCP port 1433 for MS SQL, if it is used as the default instance.
   UDP port 1434 and all (or manually selected) TCP ports for MS SQL, if it is used as a named instance.
   TCP port 10155 for a custom Plesk Migrator service performing miscellaneous tasks.
   TCP port 10156 for rsync server.
   TCP port 8443 for access to Plesk XML API on the target server and on the source servers, if migrating from Plesk.
   TCP ports 110, 143 for POP3 and IMAP, on source and target servers. These are used for post-migration checks.

   C:\> telnet source_server_IP port_number

   C:\> PortQry.exe -n source_server_IP -p TCP -o port_number

3. Ensure that UAC (User Account Control) is disabled in case if username provided as 'administrator login' member of Administrators group, but not Windows administrator.

4. Make sure that firewall is properly configured, as it may affect communication between the source and target servers, or temporarily disable it if it does not restrict your security requirements. Enable it back once a migration is finished.
   Ensure that target server is not behind NAT and routing is configured properly.

Additional Information

Migration cannot be started: Panel Migrator failed to install RPC Agent

Migration Guide. Migration Prerequisites