Winsock connect() error 10051 - c++

Question

I get an 10051 socket error every time I try to use this code:
USES_CONVERSION;
LPTSTR addr = A2W("192.168.1.209");
m_pSMACLPRCli = new CSMACLPRCli(addr, 12010, m_hWnd);
m_pSMACLPRCli->StartThread();
This is the constructor for m_pSMACLPRCli:
CSMACLPRCli::CSMACLPRCli(LPTSTR lpsztIPAddress, int nPort, HWND hParentWnd)
And this is how I create the socket and connect:
void CBlockingSocket::Create(int nType /* = SOCK_STREAM */)
{
ASSERT(m_hSocket == NULL);
if ((m_hSocket = socket(AF_INET, nType, 0)) == INVALID_SOCKET)
{
TRACE("\n Socket Error !1 (%d)\n", WSAGetLastError());
int err = WSAGetLastError();
}
}
BOOL CBlockingSocket::Connect(LPCSOCKADDR psa)
{
ASSERT(m_hSocket != NULL);
// should timeout by itself
if (connect(m_hSocket, psa, sizeof(SOCKADDR)) == SOCKET_ERROR)
{
int nLastErr = WSAGetLastError();
return FALSE;
}
return TRUE;
}
The real funny thing is that when I use the exact same code, class structure etc. in a VS2008 project, everything works as expected, but when I use it in a VS2010 project, at connect() I get a 10051 error, Network is unreachable.
EDIT: The original VS2010 proj. is compiled using UNICODE. I've made a new VS2010 using MULTI-BYTE for testing and the connect() method returns no error, and ... connects. Could it be something wrong with my way of passing the address string to the constructor?
USES_CONVERSION;
LPTSTR addr = A2W("192.168.1.209");
m_pSMACLPRCli = new CSMACLPRCli(addr, 12010, m_hWnd);
m_pSMACLPRCli->StartThread();
SOLVED:
The real problem was not the connect() method, but had to do with my way of passing the address string to a constructor of a sockaddr object.
The constructor:
CSockAddr(const char *pchIP, const USHORT ushPort = 0) // dotted IP addr string
{
sin_family = AF_INET;
sin_port = htons(ushPort);
sin_addr.s_addr = inet_addr(pchIP);
}
Constructor call used by me:
CString m_strSrvIPAddr;
CSockAddr saServer((char *) LPTSTR(LPCTSTR(m_strSrvIPAddr)), USHORT(m_nPort));
I changed the call to this:
CStringA strAddr(m_strSrvIPAddr);
CSockAddr saServer((const char *) strAddr, USHORT(m_nPort));
So I had to do a conversion of the string from UNICODE to MULTI_BYTE.

Answer 1

When calling connect(), you need to use sizeof(SOCKADDR_IN) or sizeof(SOCKADDR_IN6) depending on what psa is actually pointing at. I would suggest having the caller pass in the actual size value:
BOOL CBlockingSocket::Connect(LPCSOCKADDR psa, int sasize)
{
ASSERT(m_hSocket != INVALID_SOCKET);
// should timeout by itself
if (connect(m_hSocket, psa, sasize) == SOCKET_ERROR)
{
int nLastErr = WSAGetLastError();
return FALSE;
}
return TRUE;
}
SOCKADDR_IN sa;
...
Connect((LPSOCKADDR)&sa, sizeof(sa));
Alternatively, it would be better to use SOCKADDR_STORAGE and just type-cast it when passing it to connect():
BOOL CBlockingSocket::Connect(const SOCKADDR_STORAGE *psa)
{
ASSERT(m_hSocket != INVALID_SOCKET);
// should timeout by itself
if (connect(m_hSocket, (LPCSOCKADDR)psa, sizeof(SOCKADDR_STORAGE)) == SOCKET_ERROR)
{
int nLastErr = WSAGetLastError();
return FALSE;
}
return TRUE;
}
SOCKADDR_STORAGE sa;
...
Connect(&sa);

Answer 2

It seems that this problem is not related to your code or the development environment but rather to the network the computer is connected to.
The output of ipconfig will let you know your IP address and the subnet mask which will allow you to understand which network you belong to.
The 192.186.0.0 network is a local address (behind a NAT) and you will not be able to connect to an address on this network unless you are part of it. If your IP address does not start with 192.168 it is the cause for the error you're getting.