COMSTAT

The COMSTAT instruction retrieves the status of the communications device. The instruction uses the following format:

Where:

label

Optional. A Program Execution Label.

comfile

Required. A previously defined and opened COMFILE definition.

status

Required. A Character String Variable that receives the status information.

Flags Affected: EOS

Note the following:

1. The {comfile} variable specifies the device that is interrogated. The {comfile} must have been previously opened via the COMOPEN instruction.

2. The EOS flag is set if status information is lost due to the {status} being too small.

3. The following information is returned for local ports. Not all information is returned under Windows. Some values may be correct but are documented as having a problem (Maybe ?).

 

Byte	Value	Description
1-8		Port Status
1	Always 0	Time-out occurred if ‘1’
2	Always 1	Transmission shift register empty if ‘1’
3	Always 1	Transmission hold register empty if ‘1’
4		Break detected if ‘1’
5		Framing error if ‘1’
6		Parity error if ‘1’
7		Overrun error if ‘1’
8		Data ready if ‘1’
9-16		Modem status
9		Receive line signal detected if ‘1’
10	Maybe ?	Ring indicate if ‘1’
11		Data set ready if ‘1’
12		Clear to send if ‘1’
13		Change in receive line signal detected if ‘1’
14	Maybe ?	Trailing edge ring indicator if ‘1’
15		Change in data set ready if ‘1’
16		Change in clear to send status if ‘1’
17-21		Character count of last COMWRITE/COMREAD
22		Status of data terminal ready signal

 

4. The following information is returned for Windows sockets:

 

Byte	Description
1	Zero (0) if not connected or one (1) if connected
2	Zero if writing is disabled or one if writing is enabled
3	Zero if reading is disabled or one if reading is enabled
4	Zero if no error or one if error occurred
5-12	Last generic error code
13-20	Last native error code
21	Zero if no socket attach request is pending or one if a request is pending

 

5. The following information is returned for RMS pipes:

 

Byte	Description
1	Zero (0) if not connected or one (1) if connected
2	Zero if writing is not available or one if writing is available
3	Zero if no data to read or one if data is available
4	Zero if no error or one if error occurred
5-12	Last generic error code
13-20	Last native error code

 

6. Generic error codes that can occur for sockets, pipes, or opened file/devices are:

 

Code	Description
0	No error.
1	No more write buffer space.
2	A write is already in progress.
3	Not connected to another process.
4	Send failed.
5	Receive failed.
6	Unexpected API error.
7	Unread data exists.
8	Timeout during send

 

7. When using a Linux runtime where the {comfile} is opened for a file/device, the following information is returned:

 

Byte	Description
1	Zero (0) if not opened or one (1) if opened.
2	Zero if writing is not available or one if writing is available.
3	Zero if no data to read or one if data is available.
4	Zero if no error or one if error occurred.
5-12	Last generic error code.
13-20	Last native error code

See Also: Communication I/O Instructions