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ComDBClaimNextFreePort returns the lowest COM port number that is not already in use.
Syntax
LONG ComDBClaimNextFreePort(
[in] HCOMDB HComDB,
[out] LPDWORD ComNumber
);
Parameters
[in] HComDB
Handle to the COM port database that is returned by ComDBOpen.
[out] ComNumber
Pointer to the COM port number that the routine returns to the caller. This pointer must be non-NULL. A port number is an integer that ranges from 1 to COMDB_MAX_PORTS_ARBITRATED.
Return value
ComDBClaimNextFreePort returns one of the following status values.
| Return code | Description |
|---|---|
|
The routine successfully returned a COM port number. |
|
The routine could not write to the database. |
|
The specified COM port database handle is not valid. |
|
The database cannot arbitrate any more port numbers. |
|
The routine could not access the database. To get extended error information, call GetLastError. |
|
An internal error occurred; call GetLastError to get extended error information. |
Remarks
Claiming a COM port number in the COM port database logs the port number as "in use". Note that the database does not contain information about the caller or device that claims a port number.
ComDBClaimNextFreePort runs in user mode.
For more information, see Obtaining and Releasing a COM Port Number.
Requirements
| Requirement | Value |
|---|---|
| Target Platform | Desktop |
| Header | msports.h (include Msports.h) |
| Library | Msports.lib |
| DLL | Msports.dll |