SIMATIC 3964R protocol for Windows 9x/XP/7 
Installation Manual, 01/2013, J31069-D0131-U001-A2-7218 
13
 
Programming interface 
4
4.1  Functions of the serial interface 
 
 
Note 
You will find all the error messages listed in this section in the section "Error and status 
messag
es (Page 23)". 
 
ComOpen 
 
comInt 
ComOpen
  (LPCSTR com_name,  
int read_number,  
int write_number,  
HWND hwnd) 
This function is used to open an interface and to prepare for data transfer. It must be called 
before all other functions. 
 
Parameter 
com_name  Interface name as string  
Possible values "COM1 ... COM255"; a maximum of 4 COM ports can be 
open at the same time 
read_number  Size of the receive buffer in bytes 
write_number  Size of the send buffer in bytes 
hwnd  Windows handle as destination for the notification message 
 
 
Return value 
≥ 0  Handle for the opened interface 
< 0  possible error message: 
•  COM_ALREADY_OPEN 
•  COM_DDFINI_ERROR 
•  COM_NO_MEMORY 
•  COM_NO_HANDLE 
•  COM_REGISTRY 
•  COM_NO_CONFIG