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ComDBClaimNextFreePort function (msports.h)

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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
ERROR_SUCCESS
 The routine successfully returned a COM port number.
ERROR_CANTWRITE
 The routine could not write to the database.
ERROR_INVALID_PARAMETER
 The specified COM port database handle is not valid.
ERROR_NO_LOG_SPACE
 The database cannot arbitrate any more port numbers.
ERROR_NOT_CONNECTED
 The routine could not access the database. To get extended error information, call GetLastError.
ERROR_Xxx
 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

See also

ComDBClaimPort

ComDBReleasePort