Trying to Retrieve a List of Active Serial/Com Ports

[kudruu]

Hi,
I am trying to find a way to populate a list of active Com ports on a
computer. There may be around 30 on one computer and all connected to
different Buses but I am looking for one in particular that is
emitting packets that I need to monitor.
Is there a function in C (maybe using winAPI) that will return the
list of com ports?

Another question I have is whether I am using CreateFile correctly.
For debugging purposes you can see I have declared "char
activecomports" to contain three com ports that I have on my current
computer, although there is nothing connected to them, I expect the
program to cycle through them anyway.
The program runs until the first action after the do{} loop (nBuf =
read1...) where it halts and does not continue, am I passing in my com
ports incorrectly or does my "fd" value get messed up somewhere? Here
is the relevant code I am using:

char comPort[20];
UCHAR *adrs; //This is an unsigned char
time_t TimeSec = 0;

int i,j,udi,k, nBuf, readAgain=0;
int Msg_ID, length, elmThree;
const char *activecomports[3] = {"COM1", "COM3", "COM4"};
for (i=0; i<4;i++)
{

(HANDLE)fd[0] = CreateFile(&act ivecomports[i][0], GENERIC_READ, 0,
0, OPEN_EXISTING, FILE_ATTRIBUTE_ NORMAL, 0 );
if( (HANDLE)fd[0] == INVALID_HANDLE_ VALUE ) {
printf("CreateF ile error");
exit(0);
}
do {

nBuf = read1( fd[0], (buf[0]+nData[0]), (RS232BUFSIZ-nData[0]) );

if( nBuf 0 ) {
nData[0] += nBuf;
readAgain = ( nData[0] == RS232BUFSIZ );
while( (i = findNextPacket( TimeSec, buf[0], &strt[0],
&nData[0] )) != -1 ) {
Msg_ID = *(buf[0]+i+1);
length = *(buf[0]+i+2);
elmThree = *(buf[0]+i+3);
adrs = buf[0]+i+4;
switch( Msg_ID ) {
default:
continue;
case EVENT_MSG_TYPE:
break;
} } }
} while( readAgain );
}
updateConnectio n( (HANDLE)fd[0] );

int read1( int fd, UCHAR *buf, int bufSiz ) {
int nBytesRead;
ReadFile( (HANDLE)fd, (LPVOID)buf, (DWORD)bufSiz,
(LPDWORD)&nByte sRead, NULL );
return nBytesRead;
}

Thank you so much in advance for any help you can provide!

[Richard Tobin]

In article <11************ *********@z28g2 000prd.googlegr oups.com>,
<ku****@gmail.c omwrote:

(HANDLE)fd[0] = CreateFile( comPort,

....

>This syntax works.

Only because your compiler accepts non-standard C. Casts aren't
allowed on the target of an assignment. Assuming that int is suitable
for storing a pointer in your implementation (which presumably it is),

fd[0] = (int)CreateFile ( comPort,

would be correct.

-- Richard
--
"Considerat ion shall be given to the need for as many as 32 characters
in some alphabets" - X3.4, 1963.

[Johan Bengtsson]

ku****@gmail.co m wrote:

On Jun 21, 2:09 pm, [e-mail] c-cnrc.gc.ca (Walter Roberson)
wrote:

>In article <1182455915.107 661.103...@i13g 2000prf.googleg roups.com>,

Your code showed no definition for fd, and no information
about the type or macro HANDLE. Syntatically, it appears that you
are coverting the type of fd[0] *after* the assignment, which
seems like a waste of effort.

>>Thank you so much in advance for any help you can provide!

Lots of undefined stuff there. Looks suspiciously like Windows
specific.

Thanks for your input...
fd is defined in the same document as a public: int fd[2] = {-1,-1};
CreateFile returns type HANDLE which is another winAPI defined type
and is built with an AutoClose function so I keep fd as an int both
for the invalid definition, and for a kind of ease while passing it
around to functions (was having trouble passing HANDLE types before).

What would be wrong with declaring it like this:

HANDLE fd[2]={NULL,NULL};