InetTelnetWrite, NON-FATAL RUN-TIME ERROR: System socket error

Hi

I'm using different telnet devices on my test system. Some times I'm running into an error: "NON-FATAL RUN-TIME ERROR:   "R905BB_FOSEM.c", line 154, col 15, thread id 5972:   Function InetTelnetWrite: (return value == -4 [0xfffffffc]). System socket error"

At the actual situation hTelnet is 29.  If I call the function again, it works ok and the program continious.

{
    int  err, iBytes, hTelnet = -999;

   Delay(0.5);          
    hTelnet = FOSM_OpenTelnet (ipServer, NULL, 0);

    P_Delay(2.0);

    if((err = InetTelnetWrite(hTelnet, "RST", "\r\n", -1, &iBytes,  2000)) != 0)
        return err;
    err = InetTelnetClose (hTelnet);
    return err;
}

 Kind regards

Andreas