Since SmartConnect uses the WinHTTP by Microsoft here is a provisional list of errorcodes:
12178 Returned by WinHttpGetProxyForUrl when a proxy for the specified URL cannot be located.
12180 Returned by WinHttpDetectAutoProxyConfigUrl if WinHTTP was unable to discover the URL of the Proxy Auto-Configuration (PAC) file.
12166 An error occurred executing the script code in the Proxy Auto-Configuration (PAC) file.
12103 Returned by the HttpRequest object if a specified option cannot be requested after the Open method has been called.
12102 Returned by the HttpRequest object if a requested operation cannot be performed after calling the Send method.
12100 Returned by the HttpRequest object if a requested operation cannot be performed before calling the Open method.
12101 Returned by the HttpRequest object if a requested operation cannot be performed before calling the Send method.
12029 Returned if connection to the server failed.
The server requires SSL client Authentication. The application retrieves the list of certificate issuers by calling WinHttpQueryOption with the WINHTTP_OPTION_CLIENT_CERT_ISSUER_LIST option. For more information, see the WINHTTP_OPTION_CLIENT_CERT_ISSUER_LIST option. If the server requests the client certificate, but does not require it, the application can alternately call WinHttpSetOption with the WINHTTP_OPTION_CLIENT_CERT_CONTEXT option. In this case, the application specifies the WINHTTP_NO_CLIENT_CERT_CONTEXT macro in the lpBuffer parameter of WinHttpSetOption. For more information, see the WINHTTP_OPTION_CLIENT_CERT_CONTEXT option. Windows Server 2003 with SP1 and Windows XP with SP2: This error is not supported.
The application does not have the required privileges to access the private key associated with the client certificate. Windows Server 2003 with SP1 and Windows XP with SP2: This error is not supported.
The context for the SSL client certificate does not have a private key associated with it. The client certificate may have been imported to the computer without the private key. Windows Server 2003 with SP1 and Windows XP with SP2: This error is not supported.
12183 Returned by WinHttpReceiveResponse when an overflow condition is encountered in the course of parsing chunked encoding.
12044 Returned by WinHttpReceiveResponse when the server requests client authentication. Windows Server 2003 with SP1 and Windows XP with SP2: This error is not supported.
12030 The connection with the server has been reset or terminated, or an incompatible SSL protocol was encountered. For example, WinHTTP version 5.1 does not support SSL2 unless the client specifically enables it.
12155 Obsolete; no longer used.
12181 Returned by WinHttpReceiveResponse when a larger number of headers were present in a response than WinHTTP could receive.
12150 The requested header cannot be located.
12182 Returned by WinHttpReceiveResponse when the size of headers received exceeds the limit for the request handle.
12019 The requested operation cannot be carried out because the handle supplied is not in the correct state.
12018 The type of handle supplied is incorrect for this operation.
12004 An internal error has occurred.
12009 A request to WinHttpQueryOption or WinHttpSetOption specified an invalid option value.
12154 Obsolete; no longer used.
12152 The server response cannot be parsed.
12005 The URL is not valid.
12015 The login attempt failed. When this error is encountered, the request handle should be closed with WinHttpCloseHandle. A new request handle must be created before retrying the function that originally produced this error.
12007 The server name cannot be resolved.
12172 Obsolete; no longer used.
12017 The operation was canceled, usually because the handle on which the request was operating was closed before the operation completed.
12011 The requested option cannot be set, only queried.
12001 Obsolete; no longer used.
12156 The redirection failed because either the scheme changed or all attempts made to redirect failed (default is five attempts).
12032 The WinHTTP function failed. The desired function can be retried on the same request handle.
12184 Returned when an incoming response exceeds an internal WinHTTP size limit.
12038 Returned when a certificate CN name does not match the passed value (equivalent to a CERT_E_CN_NO_MATCH error).
12037 Indicates that a required certificate is not within its validity period when verifying against the current system clock or the timestamp in the signed file, or that the validity periods of the certification chain do not nest correctly (equivalent to a CERT_E_EXPIRED or a CERT_E_VALIDITYPERIODNESTING error).
12057 Indicates that revocation cannot be checked because the revocation server was offline (equivalent to CRYPT_E_REVOCATION_OFFLINE).
12170 Indicates that a certificate has been revoked (equivalent to CRYPT_E_REVOKED).
12179 Indicates that a certificate is not valid for the requested usage (equivalent to CERT_E_WRONG_USAGE).
12157 Indicates that an error occurred having to do with a secure channel (equivalent to error codes that begin with "SEC_E_" and "SEC_I_" listed in the "winerror.h" header file).
12175 One or more errors were found in the Secure Sockets Layer (SSL) certificate sent by the server. To determine what type of error was encountered, check for a WINHTTP_CALLBACK_STATUS_SECURE_FAILURE notification in a status callback function. For more information, see WINHTTP_STATUS_CALLBACK.
12045 Indicates that a certificate chain was processed, but terminated in a root certificate that is not trusted by the trust provider (equivalent to CERT_E_UNTRUSTEDROOT).
12169 Indicates that a certificate is invalid (equivalent to errors such as CERT_E_ROLE, CERT_E_PATHLENCONST, CERT_E_CRITICAL, CERT_E_PURPOSE, CERT_E_ISSUERCHAINING, CERT_E_MALFORMED and CERT_E_CHAINING).
12012 The WinHTTP function support is being shut down or unloaded.
12002 The request has timed out.
12167 The PAC file cannot be downloaded. For example, the server referenced by the PAC URL may not have been reachable, or the server returned a 404 NOT FOUND response.
12006 The URL specified a scheme other than "http:" or "https:".
Not enough memory was available to complete the requested operation. Header: Declared in Winerror.h
The size, in bytes, of the buffer supplied to a function was insufficient to contain the returned data. For more information, see the specific function. Header: Declared in Winerror.h
The handle passed to the application programming interface (API) has been either invalidated or closed. Header: Declared in Winerror.h
No more files have been found. Header: Declared in Winerror.h
No more items have been found. Header: Declared in Winerror.h
The required protocol stack is not loaded and the application cannot start WinSock. Header: Declared in Winerror.h