8 extra bytes before message

A customer of ours is using a DIGI PortServer TS4 in RealPort mode, and a COM port redirector on WinXP.

For some reason, whenever the embedded device connected to the PortServer transmits a message, the application running on the WinXP machine receives 8 extra bytes bef ore the actual message. The bytes typically look something like FF 7D FF FF FF FF 7D B7.

Any ideas what would cause this?

When you say “com port redirector”, are you referring to our Realport software or some other company’s com port redirection software?

The data appears to be Telnet ascii data, so if this com port redirection software is connecting directly to the serial port of the Digi via TCP port 200x, try 210x instead (where x is number of the physical port on your TS4).

We are using Digi’s Realport software.

We now know that the problem disappears if we shorten the cable to less than 50 feet, or reduce the baud rate from 38400 to 9600.

You may wish to check the rs232 serial specifications for cables at this link: