RealPort Long “Dead” Connection Timeouts.

Summary

Under default RealPort client configuration, only one client may hold a given port open at a time. If that client’s TCP session becomes inactive or loses connectivity without a clean TCP teardown, it can take 15–20 minutes (default TCP retry/timeout behavior) for the connection to be detected as dead. During this window, new clients cannot access the port because the device still considers the original session active.

In some cases, this clears faster when the original session receives a TCP RST (forcible close), which explains intermittent successful retests.

Symptoms

• Attempting to open a RealPort-mapped serial port from a second client fails or hangs while another client previously connected.
• Port becomes accessible again only after a long delay (typically 15–20 minutes), or immediately if the original session is forcibly reset (TCP RST observed).
• Intermittent behavior: sometimes reconnects quickly, sometimes delayed significantly.

Resolution (Mitigation)

Enable Exclusive Mode in the RealPort configuration.

Configuration>Services>RealPort>Exclusive Mode

The way to mitigate this is to enable “exclusive” mode in the RealPort configuration. This will cause new connections to forcibly close any connections from the same IP address. This works if only a single client is expected to connect to the device but would not necessarily prevent delays in a multi-client scenario if the original holder fails to reconnect.