Problem with ListAvailableSQLServers in vb 6

Hello,
I have got a very strange problem...
In VB6, in the beginning of my application, I make a
ListAvailableSQLServers to see what MSDE servers are on the network for
my application.
The problem is that if a computer is disconnected from the network, but
has MSDE working (a laptop) then the ListAvailableSQLServers will return
no server, even if there is a local server.
Is there something to do to have it?
PS : In VB6, I use
dim ListSvr as collection
Set ListSvr = SQLDMO.ListAvailableSQLServers
and the count is 0
I have also tried with
Dim oServer As New SQLDMO.SQLServer2
Dim oNameList As SQLDMO.NameList
Set oNameList = oServer.Application.ListAvailableSQLServers '
and oNameList.Count is still 0
Can you please help me?
Thank you
Marc Allard
Allcomp
hi Marc,
"Allcomp" <marc@.nospam.allcomp.be> ha scritto nel messaggio
news:41d95753$0$329$ba620e4c@.news.skynet.be
> Hello,
> I have got a very strange problem...
> In VB6, in the beginning of my application, I make a
> ListAvailableSQLServers to see what MSDE servers are on the network
> for my application.
> The problem is that if a computer is disconnected from the network,
> but has MSDE working (a laptop) then the ListAvailableSQLServers will
> return no server, even if there is a local server.
> Is there something to do to have it?
> PS : In VB6, I use
> dim ListSvr as collection
> Set ListSvr = SQLDMO.ListAvailableSQLServers
> and the count is 0
> I have also tried with
> Dim oServer As New SQLDMO.SQLServer2
> Dim oNameList As SQLDMO.NameList
> Set oNameList = oServer.Application.ListAvailableSQLServers '
> and oNameList.Count is still 0
>
can you please verify your local MSDE instance has network protocols enabled
via Server Network Utility (svrnetcn.exe)?
if network protocols are disabled (default for MSDE installation), the
relative instance will not be enlisted in the broadcast call for server
enumeration..
as regard ListAvailableServer method provided by SQL-DMO object model, I've
found during my (little) experience, this sort of rules:
ListAvailableServer uses ODBC function SQLBrowseConnect() provided by ODBC
libraries installed by Mdac;
this is a mechanism working in broadcast calls, which result never are
conclusive and consistent, becouse results are influenced of various
servers's answer states, answer time, etc.
Until Mdac 2.5, SQLBrowseConnect function works based on a NetBIOS
broadcast, on which SQL Servers respond (Default protocol for SQL Server
7.0), while in SQL Server 2000 the rules changed, because the default client
protocol changed to TCP/IP and now a UDP broadcast is used, beside a NetBIOS
broadcast, listening on port 1434:
which is using a UDP broadcast on port 1434, if instance do not listen or
not respond on time they will not be part of the enumeration.
Some basic rules for 7.0 are:
- SQL Servers have to be running on Windows NT or Windows 2000 and have to
listen on Named Pipes, that is why in 7.0 Windows 9x SQL Servers will never
show up, because they do not listen on Named Pipes.
- The SQL Server has to be running in order to respond on the broadcast.
There is a gray window of 15 minutes after shutdown, where a browse master
in the domain may respond on the broadcast and answer.
- If you have routers in your network, that do not pass on NetBIOS
broadcasts, this might limit your scope of the broadcast.
- Only servers within the same NT domain (or trust) will get enumerated.
In SQL Server 2000 using MDAC 2.6 this changes a little, because now the
default protocol has been changed to be TCP/IP sockets and instead of a
NetBIOS broadcast, they use a TCP UDP to detect the servers. The same logic
still applies roughly.
- SQL Server that are running
- SQL Server that listening on TCP/IP
- Running on Windows NT or Windows 2000 or Windows 9x
- If you use routers and these are configured not to pass UDP broadcasts,
only machines within the same subnet show up.
Upgrading to Service Pack 2 of SQL Server 2000 is required in order to have
..ListAvailableServer method to work properly, becouse precding release of
Sql-DMO Components of Sql Server 2000 present a bug in this area.
Courtesy of Mr. Gert E.R. Drapers
further Information at
http://sqldev.net/misc.htm
The Service Pack 3a introduced some new amenity in order to prevent MSDE
2000 to be hit by Internet worms like Slammer and Saphire virus and to
increase security, so that Microsoft decided to default for disabling
SuperSockets Network Protocols on new MSDE 2000 installation.
Instances of SQL Server 2000 SP3a or MSDE 2000 SP3a will stop listening on
UDP port 1434 when they are configured to not listen on any network
protocols. This will stop enlisting these servers.
The latest problem has been added by Windows XP service pack 2, which
implements a strong protection of the local computer closing all ports for
incoming and outgoing connections, requiring to manually open the desired IP
port in order to allow external remote connections
Andrea Montanari (Microsoft MVP - SQL Server)
http://www.asql.biz/DbaMgr.shtmhttp://italy.mvps.org
DbaMgr2k ver 0.9.1 - DbaMgr ver 0.55.1
(my vb6+sql-dmo little try to provide MS MSDE 1.0 and MSDE 2000 a visual
interface)
-- remove DMO to reply
|||Hello,
My enabled networks protocols are Named pipes and Tcp/IP
With EnumSQLSvr.exe, it doesn't work (when I remove the network cable, I
have no server). I have exactly the same error with Osql -L
I use WinXP SP2 without firewall for my tests.
With SQL Server 2000, a Win98 computer is in the list
I have also seen something strange...
I make the ListAvailableSQLServers
If I have a return count of 0, then I use
the object
SQLDMO.SQLServer2
Set oServer = New SQLDMO.SQLServer2
Set ListSvr = oServer.ListInstalledInstances
will return the local computer when no network is enabled.
Thank you
Marc Allard
Allcomp
Andrea Montanari wrote:
> hi Marc,
> "Allcomp" <marc@.nospam.allcomp.be> ha scritto nel messaggio
> news:41d95753$0$329$ba620e4c@.news.skynet.be
>
> can you please verify your local MSDE instance has network protocols enabled
> via Server Network Utility (svrnetcn.exe)?
> if network protocols are disabled (default for MSDE installation), the
> relative instance will not be enlisted in the broadcast call for server
> enumeration..
> as regard ListAvailableServer method provided by SQL-DMO object model, I've
> found during my (little) experience, this sort of rules:
> ListAvailableServer uses ODBC function SQLBrowseConnect() provided by ODBC
> libraries installed by Mdac;
> this is a mechanism working in broadcast calls, which result never are
> conclusive and consistent, becouse results are influenced of various
> servers's answer states, answer time, etc.
> Until Mdac 2.5, SQLBrowseConnect function works based on a NetBIOS
> broadcast, on which SQL Servers respond (Default protocol for SQL Server
> 7.0), while in SQL Server 2000 the rules changed, because the default client
> protocol changed to TCP/IP and now a UDP broadcast is used, beside a NetBIOS
> broadcast, listening on port 1434:
> which is using a UDP broadcast on port 1434, if instance do not listen or
> not respond on time they will not be part of the enumeration.
> Some basic rules for 7.0 are:
> - SQL Servers have to be running on Windows NT or Windows 2000 and have to
> listen on Named Pipes, that is why in 7.0 Windows 9x SQL Servers will never
> show up, because they do not listen on Named Pipes.
> - The SQL Server has to be running in order to respond on the broadcast.
> There is a gray window of 15 minutes after shutdown, where a browse master
> in the domain may respond on the broadcast and answer.
> - If you have routers in your network, that do not pass on NetBIOS
> broadcasts, this might limit your scope of the broadcast.
> - Only servers within the same NT domain (or trust) will get enumerated.
> In SQL Server 2000 using MDAC 2.6 this changes a little, because now the
> default protocol has been changed to be TCP/IP sockets and instead of a
> NetBIOS broadcast, they use a TCP UDP to detect the servers. The same logic
> still applies roughly.
> - SQL Server that are running
> - SQL Server that listening on TCP/IP
> - Running on Windows NT or Windows 2000 or Windows 9x
> - If you use routers and these are configured not to pass UDP broadcasts,
> only machines within the same subnet show up.
> Upgrading to Service Pack 2 of SQL Server 2000 is required in order to have
> .ListAvailableServer method to work properly, becouse precding release of
> Sql-DMO Components of Sql Server 2000 present a bug in this area.
> Courtesy of Mr. Gert E.R. Drapers
> further Information at
> http://sqldev.net/misc.htm
> The Service Pack 3a introduced some new amenity in order to prevent MSDE
> 2000 to be hit by Internet worms like Slammer and Saphire virus and to
> increase security, so that Microsoft decided to default for disabling
> SuperSockets Network Protocols on new MSDE 2000 installation.
> Instances of SQL Server 2000 SP3a or MSDE 2000 SP3a will stop listening on
> UDP port 1434 when they are configured to not listen on any network
> protocols. This will stop enlisting these servers.
> The latest problem has been added by Windows XP service pack 2, which
> implements a strong protection of the local computer closing all ports for
> incoming and outgoing connections, requiring to manually open the desired IP
> port in order to allow external remote connections
|||If you have no network this is expected, since the enumeration is based on a
UDP (TCP) broadcast. Since this is a broadcast it normally only sees
computers in the same subnet, since most routers are configured not to pass
on UDP broadcast requests.
Besides that there is a response time issue. After the request is issued the
client only waits for a certain period of time on UDP replies from the
servers that received the UDP broadcast request.
On the local machine the API does a Registry scan, which is why local
services should show up when no network is enabled. MSDE has different
Registry entries that is why these do not show.
If you want to use the same API as SQL-DMO you need to use the
ListSQLSrv.exe tool http://sqldev.net/misc/ListSQLSvr.htm EnumSQLSvr, uses
the OLE-DB based API, which theoretically should provide the same results,
but you never know.
On Win98 I think they only enumerate local instances as far as I know.
GertD@.SQLDev.Net
Please reply only to the newsgroups.
This posting is provided "AS IS" with no warranties, and confers no rights.
You assume all risk for your use.
Copyright SQLDev.Net 1991-2004 All rights reserved.
"Allcomp" <marc@.nospam.allcomp.be> wrote in message
news:41da4402$0$316$ba620e4c@.news.skynet.be...[vbcol=seagreen]
> Hello,
> My enabled networks protocols are Named pipes and Tcp/IP
> With EnumSQLSvr.exe, it doesn't work (when I remove the network cable, I
> have no server). I have exactly the same error with Osql -L
> I use WinXP SP2 without firewall for my tests.
> With SQL Server 2000, a Win98 computer is in the list
> I have also seen something strange...
> I make the ListAvailableSQLServers
> If I have a return count of 0, then I use
> the object
> SQLDMO.SQLServer2
> Set oServer = New SQLDMO.SQLServer2
> Set ListSvr = oServer.ListInstalledInstances
> will return the local computer when no network is enabled.
>
> Thank you
> Marc Allard
> Allcomp
>
>
>
>
> Andrea Montanari wrote:
|||Hello,
In fact, I was thinking that when I remove the computer from the
network, it is able to see itself (by UDP) you can answer to yourself
(but it seem that it is not possible)?
So I think I will have to list all the local instances if I can see no
network.
PS : Win 98 can see any server (local or networked).
Thank you
Marc Allard
Allcomp
Gert E.R. Drapers wrote:
> If you have no network this is expected, since the enumeration is based on a
> UDP (TCP) broadcast. Since this is a broadcast it normally only sees
> computers in the same subnet, since most routers are configured not to pass
> on UDP broadcast requests.
> Besides that there is a response time issue. After the request is issued the
> client only waits for a certain period of time on UDP replies from the
> servers that received the UDP broadcast request.
> On the local machine the API does a Registry scan, which is why local
> services should show up when no network is enabled. MSDE has different
> Registry entries that is why these do not show.
> If you want to use the same API as SQL-DMO you need to use the
> ListSQLSrv.exe tool http://sqldev.net/misc/ListSQLSvr.htm EnumSQLSvr, uses
> the OLE-DB based API, which theoretically should provide the same results,
> but you never know.
> On Win98 I think they only enumerate local instances as far as I know.
> GertD@.SQLDev.Net
> Please reply only to the newsgroups.
> This posting is provided "AS IS" with no warranties, and confers no rights.
> You assume all risk for your use.
> Copyright SQLDev.Net 1991-2004 All rights reserved.
> "Allcomp" <marc@.nospam.allcomp.be> wrote in message
> news:41da4402$0$316$ba620e4c@.news.skynet.be...
>
>
|||If you use SQLBrowseConnect directly (not SQL-DMO) you can point it at a
single machine, which would give you this.
If you try the ListSQLSvr.exe tool with -S <your machine name> -X it will
give you a listing of your local servers only.
If you install a loopback adapter the UDP broadcast will work locally.
Good to know that Win98 does local and remote, I never touch that OS, since
NT was introduced I left DOS behind me.
GertD@.SQLDev.Net
Please reply only to the newsgroups.
This posting is provided "AS IS" with no warranties, and confers no rights.
You assume all risk for your use.
Copyright SQLDev.Net 1991-2004 All rights reserved.
"Allcomp" <marc@.nospam.allcomp.be> wrote in message
news:41da6e27$0$338$ba620e4c@.news.skynet.be...[vbcol=seagreen]
> Hello,
> In fact, I was thinking that when I remove the computer from the network,
> it is able to see itself (by UDP) you can answer to yourself (but it seem
> that it is not possible)?
> So I think I will have to list all the local instances if I can see no
> network.
> PS : Win 98 can see any server (local or networked).
> Thank you
> Marc Allard
> Allcomp
> Gert E.R. Drapers wrote:
|||Hello,
Thank you for your help
In fact, I must use Win98 because a lot of my custommers use Win98 and
don't want to change.
Marc Allard
Allcomp
Gert E.R. Drapers wrote:
> If you use SQLBrowseConnect directly (not SQL-DMO) you can point it at a
> single machine, which would give you this.
> If you try the ListSQLSvr.exe tool with -S <your machine name> -X it will
> give you a listing of your local servers only.
> If you install a loopback adapter the UDP broadcast will work locally.
> Good to know that Win98 does local and remote, I never touch that OS, since
> NT was introduced I left DOS behind me.
> GertD@.SQLDev.Net
> Please reply only to the newsgroups.
> This posting is provided "AS IS" with no warranties, and confers no rights.
> You assume all risk for your use.
> Copyright SQLDev.Net 1991-2004 All rights reserved.
> "Allcomp" <marc@.nospam.allcomp.be> wrote in message
> news:41da6e27$0$338$ba620e4c@.news.skynet.be...
>