Port.WriteLine() truncates lines > c.100 long

[brewmanz]

I installed com0com 2.0 several weeks ago and it used to work until yesterday. No changes except maybe 'regular' WinXP updates. Now it truncates lines > about 100 chars. reboot changed nothing. I uninstalled 2.0, installed 2.1 and same problem.
I have 4 pairs all set up identically:
COM90-COM91,
emuBR?  Y - N
enBuOv? N - Y
Plugin? N - N
Excl?   Y - Y
Hidden? N - N
COM80-COM81,
COM70-COM71 &
COM60-COM6 (yes, I reduced 61 to 6 so my receiver can find it).
I have a console app that opens o/p COM90 9600-N-1,COM80 9600-N-1,COM70 4800-N-1 & COM60 4800-N-1, then opens all enumerated ports, looks for GPS string (which it finds on COM5), then reads on COM5 and writelines 128 char string on COM90 & COM80, then length 300-ish strings on COM70 & COM60. The very first write to very first output port (COM90) is truncated to about 100 chars, as verified via Hyperterm. splitting string to <=90 chars and Write + final WriteLine works just fine, but is too slow :-(
Opening steps:
            SerialPort result = new SerialPort();
            try
            {
                result.PortName = aPortName; // "COM90" etc
                result.NewLine = "\r\n";
                result.ReadTimeout = 1200;
                result.WriteTimeout = 100;
                result.BaudRate = 9600; // or 4800
                result.DataBits = 8;
                result.Parity = Parity.None;
                result.StopBits = StopBits.One;
                result.Open();

following code is work-around that works on writing:
        const int kMaxWriteLen = 90;
        private static void TransmitLineToPort(string aLine, SerialPort aPort)
        {
            // problem with truncatd lines
            int pos = 0;
            string frag;
            while (pos < aLine.Length)
            {
                int fragLen = aLine.Length - pos;
                if (fragLen > kMaxWriteLen)
                    fragLen = kMaxWriteLen;
                frag = aLine.Substring(pos, fragLen);
                pos += fragLen;
                if (pos >= aLine.Length)
                    aPort.WriteLine(frag);
                else
                    aPort.Write(frag);
            }
        }

I'm using C#/dotNet 2.0.50727 SP1/VS2005 Std Ed, on WinXP Pro SP3 on HP Compaq nx6125 notebook.

Any ideas?
Thanks.

Brewmanz

[brewmanz]

The Write Timeout seems important here - okay, maybe I changed that whilst trying to tune things. With Write T/O of 10 (rather than 100), only about 14 chars of each line get written, but there is no Timeout Exception raised - it is an insidious truncation. I'll raise the timeout to 1200 & see how it goes. I thought that with a 2K write buffer things would get written almost instantly.
So, there's still a problem somewhere with writes only being slowly written into the write buffer.

[Vyacheslav Frolov]

> but there is no Timeout Exception raised - it is an insidious truncation.

At least it's raised with C++/dotNet 2.0.50727 (I'm not use C#).

Try something like this:

     private static void TransmitLineToPort(string aLine, SerialPort aPort)
     {
        try
        {
            Console.WriteLine(Sending...);
            aPort.WriteLine(aLine);
            Console.WriteLine("OK");
        }
        catch (TimeoutException) {
            Console.WriteLine("FAIL");
        }
     }