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VB Forum / General 2 / November 2004EnumPrinterDrivers fails when enum on Win9x
I'm calling the EnumPrinterDrivers function on a WinXP system. For the first parameter I'm passing in the name of a Windows ME computer residing on the network. The MSDN indicates this is perfectly acceptable. The function fails with an error 1722 (RPC unavailable). This seems odd to me as other APIs that access this WinME system on the network function properly. The EnumPrinterDrivers function has no issues when run on the local system or when accessing a NT based system across the network. sCompName$ = "\\jaguar" 'jaguar being the Windows ME computer name on the network. Also tried w/o backslashes. sDriverEnvironment$ = vbNullString Call EnumPrinterDrivers(sCompName$, sDriverEnvironment$, DRIVER_LEVEL3, 0, 0, lRequired&, lEntries&) As stated, other APIs that access this ME computer over the network function perfectly fine and when accessing a NT based computer over the network there are no issues enumerating the printer drivers remotely. I see nothing about this issue when Googling. Does anyone know why this occurs and whether a workaround exists? Many thanks, JB Hmm ... the description of that API is "enumerates the printer drivers installed on a ***specified printer server***". Since ME can not be configured as a server to offer printer drivers for a network install, I wonder if this is the cause of the failure? The fact you have success with other NT-based machines leads me to suspect this might be the problem.  SignatureRandy Birch MS MVP Visual Basic http://vbnet.mvps.org/ : I'm calling the EnumPrinterDrivers function on a WinXP system. For the first : parameter I'm passing in the name of a Windows ME computer residing on the [quoted text clipped - 21 lines] : : JB Yes, I did consider that but couldn't find anything that offered further clarification. The error I get also, I think, reinforces that theory. If anyone has any further comments on this please do add them. Thanks, JW > Hmm ... the description of that API is "enumerates the printer drivers > installed on a ***specified printer server***". Since ME can not be [quoted text clipped - 36 lines] > : > : JB Any chance that "File and Printer Sharing for Microsoft Networks" is not active on the ME computer? I saw something about it being needed for some RPC calls to work. I'm not sure about ME, but I think I have seen printers attached to Win98 systems shared out over a network, and it seems to me that if you can use them, you should be able to enumerate them... | Yes, I did consider that but couldn't find anything that offered further | clarification. The error I get also, I think, reinforces that theory. [quoted text clipped - 45 lines] | > : | > : JB Well I must say, after reading your suggestion I checked and found printer sharing NOT to be enabled. So I was hopeful that was the trick. Alas, after enabling it, rebooting and then trying again it still fails with the same error <sigh>. I wish the MSDN was more specific about whether it works on 9x/ME when these platforms are called remotely. It does indicate that the API is supported on Windows 95 and higher --it just doesn't specifically state that it is not supported when calling them remotely. Though, it does leave one the impression that those platforms are supported when reading the text for the pEnvironment value. Thanks for your post. If anyone has anything further to suggest or comment please do! JW > Any chance that "File and Printer Sharing for Microsoft Networks" is not > active on the ME computer? I saw something about it being needed for [quoted text clipped - 69 lines] > | > : > | > : JB pEnvironment "Pointer to a null-terminated string that specifies the environment (for example, Windows NT x86, Windows IA64, Windows x64, Windows NT R4000, Windows NT Alpha_AXP, Windows 4.0, or Windows NT PowerPC). If this parameter is NULL, the function uses the current environment of the caller/client (not of the destination/server)." You are calling with NULL (vbNullString). That would mean you are using the "current environment of the caller", which is Windows NT (WinXP), wouldn't it? Maybe you should try the call with "Windows 4.0", which I think means pre-NT. Maybe? | Well I must say, after reading your suggestion I checked and found printer | sharing NOT to be enabled. So I was hopeful that was the trick. Alas, after [quoted text clipped - 86 lines] | > | > : | > | > : JB I did note that information in the MSDN originally and so I am passing the proper value for the remote system in question (in the case of ME it is "Windows 4.0"). This does not correct the issue. JW > pEnvironment > "Pointer to a null-terminated string that specifies the environment (for [quoted text clipped - 115 lines] > | > | > : > | > | > : JB Hi Jerry ... Are you sure you don't want the simpler EnumPrinters function rather than EnumPrinterDrivers? EnumPrinters is a mandatory function that all providers must respond to; EnumPrinterDrivers is used to "return a list of printer drivers that have been added to a specified server by calling AddPrinterDriver or AddPrinterDriverEx". It is my understanding that EnumPrinterDrivers is used to enumerate the available printers drivers that can be installed from a network server onto a machine running the environment specified under the pEnvironment variable. IOW, you're on a XP box, you query the server for "Windows NT x86" (or "All") to get the list of printers the server can install onto that XP box. You're on a 9x box you ask for "Windows 4.0". As for the RPC error, it could be the required ports on the machine are blocked or the machine has an incompatible network adapter error. Also, is there a print$ admin share on the ME machine? Finally, the XP machine must have rights to access the remote machine -- for example, on an XP -to- XP network, if the calling XP machine does not have permission to access the shares because the calling machine has not yet successfully completed a required authentication challenge, the error returned through Err.LastDllError is 1722. So in this case it's not so much an "RPC error"; it's an "error accessing the remote machine via RPC due to insufficient credentials". Methinks 1722 might be a catch-all error code. Also, have you determined that running the same code provides the expected info when the app is run locally on the ME machine with vbNullString specified as the server? There's also some EnumPrinterDrivers code at http://vbnet.mvps.org/code/enums/enumprinterdrivers.htm) which may provide some other insight. SignatureRandy Birch MS MVP Visual Basic http://vbnet.mvps.org/ Randy, Thanks for your comments. It does appear that EnumPrinters would indeed do what I need. A little more work is involved and it looks like I'd need to use a PRINTER_INFO_2 structure versus what I originally wanted; PRINTER_INFO_3. At any rate, thanks for pointing me toward another possible solution! JW > Hi Jerry ... > [quoted text clipped - 34 lines] > http://vbnet.mvps.org/code/enums/enumprinterdrivers.htm) which may provide > some other insight. |
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