Let’s view the system communication and data flow for a recording server failover. First, the cameras stream video to the recording server using different ports and protocols depending on the camera settings. The recording server then streams video to clients on port 7563. The failover server polls the state of the recording server on port 11000 using TCP at regular intervals. If the failover server determines that the recording server has failed, the failover server starts the failover procedure. In Cold Standby mode, the failover server sends a failover message to the management server on port 80 using HTTP. The management server retrieves the configuration from the SQL server on port 1433 using HTTP. The failover server then applies the configuration and takes over as the recording server. In Hot Standby mode, the failover server sends a message to the management server on port 80 using HTTP. As the Hot Standby server already has the recording server configuration loaded, it immediately starts the live camera streams and starts performing any event-based recording. The management server notifies the SQL server about the failover status on port 1433 using TCP. The management server also updates the service channel with the new information on port 80 using HTTP. The service channel sends the update message to all clients. This communication is sent on port 80 using HTTP for Windows and Active Directory users, and on port 443 using HTTPS for basic users. The clients connect to the failover server and resume viewing video from it on port 7563. Once the failover server determines the recording server is working again, the failover process reverses and the recording server takes over from the failover server. Any recordings stored on the failover server during the failover period transfer back to the recording server storage database on port 5210 using TCP. This may take some time depending on the length of the failover period. After the recordings are written to the recording server storage database, they are deleted from the failover server.