Int 2F Fn CB07  - Communicating Applications Specification - Open File     [F]

   AX = CB07h
   BX = event handle from find (AL=05h,06h) or submit task (AL=01h)
   CX = receive file number (ignored for task queue and log queue)
       0000h  open receive control file
       N      open Nth received data file
   DL = queue
       00h task queue
       01h receive queue control file or received file, as given by CX
       02h log queue
       03h group file in task queue (v1.2+)
       04h group file in log queue (v1.2+)

Return: AX = 0000h successful
       BX = DOS file handle for requested file
   AX < 0     error code (see AX=CB01h)

Note:  the returned file handle has been opened in read-only mode and should
     be closed with INT 21/AH=3Eh after use

See Also: AX=CB01h,AX=CB05h,AX=CB14h