/dev/tty read is broken!

[John E. A.]

fgetc(port) with port=/dev/ttyS0 hangs when no data is present.

I connect the serial ports of two PC's via a null modem. One running 
win2k/cygwin the other GNU/Linux.

To confirm that all h/w is working:
linux/minicom <-> win2k/hyperterm	- typing works both ways

Then two test configurations:
win2k/hyperterm <-> linux/test.c	- which works
linux/minicom <-> win2k/cygwin/test.c	- which fails as described below

With the following test program:

/*--------------------- test.c ---------------------*/

#include <stdio.h>

main ()
{
     FILE *port;
     unsigned int data = 'X';
     unsigned char *string = "Waiting for input...\r";

     port = fopen("/dev/ttyS0","w+");
     if (port == NULL) {
         perror("fopen");
         exit(1);
         }

     printf("Sending Prompt string:\n");
     fputs(string, port);
     fflush(port);

     printf("Now waiting for characters...\n");
     while (data != 'Q') {
         data = fgetc(port);
         printf("--->%c<---\n", data);
         fprintf(port, "--->%c<---\r", data);
         fflush(port);
         }

     /* close the serial port */
     fclose(port);
}

/*------------------ end of test.c ------------------*/

I step through this in gdb and it will step through the fgetc() call without 
error if a character has already been sent by the other end. However if I run 
the program full speed, or step through the fgetc() on cygwin without previously 
typing a character into minicom, then the fgetc() call hangs. I attached a text 
screen capture of this crash in gdb.

I also saw random hangs in either of the two fflush() calls that varied from 
build to build of test.c.

I have cygwin 1.3.18-1 on win2k.

I'm will try to help debug this if someone will offer guidance.

Will the /dev/tty guru (Mr. Steve O sir?) please HELP!!!

I'm desperate. This is my second post.

Thanks...

John E. A.

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