SQLBrowseConnect doesn't seem to enumerate servers on local domain - c++

Question

I am trying to enumerate local SQL instances using SQLBrowseConnect. Generally speaking, this is working fine, but we have one set up which results in an SQLExpress instance not being discovered. Here is the code in question:
SQLSetConnectAttr(hSQLHdbc,
SQL_COPT_SS_BROWSE_SERVER,
_T("(local)"),
SQL_NTS);
CString inputParam = _T("Driver={SQL Server}");
SQLBrowseConnect(hSQLHdbc,
inputParam,
SQL_NTS,
szConnStrOut,
MAX_RET_LENGTH,
&sConnStrOut);
In the failed instance, the code is running on a domain controller. The missing local instance of SQL is an SQLExpress instance (version 9). However, the puzzling thing is that running sqlcmd -L shows the missing instance without any problems.
Am I missing something really silly? Please remember that on other systems and set ups there is no issue.

Answer 1

After much investigation, I couldn't really find out what the problem was specifically. This one machine just would not discover its own instances of SQL using SQLBrowseConnect. I therefore decided to write my own version. Discovering SQL instances turns out to be pretty easy. You just send a broadcast UDP packet to port 1434 containing the payload 0x02 (1 byte) and wait for SQL servers to respond. They respond with one packet per server which details all the instances on that machine. The code required to do this is shown below:
// to enumerate sql instances we simple send 0x02 as a broadcast to port 1434.
// Any SQL servers will then respond with a packet containing all the information
// about installed instances. In this case we only send to the loopback address
// initialise
WSADATA WsaData;
WSAStartup( MAKEWORD(2,2), &WsaData );
SOCKET udpSocket;
struct sockaddr_in serverAddress;
if ((udpSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
{
return;
}
// set up the address
serverAddress.sin_family = AF_INET;
serverAddress.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
serverAddress.sin_port = htons(1434);
// the payload
char payload = 0x02;
// config the port for broadcast (not totally necessary right now but maybe in the future)
BOOL broadcast = TRUE;
setsockopt(udpSocket, SOL_SOCKET, SO_BROADCAST, reinterpret_cast<const char*>(&broadcast), sizeof(BOOL));
// receive address info
sockaddr_in RecvAddr;
RecvAddr.sin_family = AF_INET;
RecvAddr.sin_addr.s_addr = htonl(INADDR_ANY);
sockaddr_in SenderAddr;
int SenderAddrSize = sizeof (SenderAddr);
// bind the socket to the receive address info
int iResult = bind(udpSocket, (SOCKADDR *) & RecvAddr, sizeof (RecvAddr));
if (iResult != 0)
{
int a = WSAGetLastError();
return;
}
if (sendto(udpSocket, &payload, 1, 0, (struct sockaddr *) &serverAddress, sizeof(serverAddress)) < 0)
{
int a = WSAGetLastError();
return;
}
// set up a select so that if we don't get a timely response we just bomb out.
fd_set fds ;
int n ;
struct timeval tv ;
// Set up the file descriptor set.
FD_ZERO(&fds) ;
FD_SET(udpSocket, &fds) ;
// Set up the struct timeval for the timeout.
tv.tv_sec = 5 ;
tv.tv_usec = 0 ;
// Wait until timeout or data received.
n = select ( (int)udpSocket, &fds, NULL, NULL, &tv ) ;
if ( n == 0)
{
// timeout
return;
}
else if( n == -1 )
{
// error
return;
}
// receive buffer
char RecvBuf[1024];
int BufLen = 1024;
memset(RecvBuf, 0, BufLen);
iResult = recvfrom(udpSocket,
RecvBuf,
BufLen,
0,
(SOCKADDR *) & SenderAddr,
&SenderAddrSize);
if (iResult == SOCKET_ERROR)
{
int a = WSAGetLastError();
return;
}
// we have received some data. However we need to parse it to get the info we require
if (iResult > 0)
{
// parse the string as required here. However, note that in my tests, I noticed
// that the first 3 bytes always seem to be junk values and will mess with string
// manipulation functions if not removed. Perhaps this is why SQLBrowseConnect
// was having problems for me???
}