Problem Description:
A 6420 error indicates that the Advantage client's process for finding the Advantage Database Server has failed. To communicate with 32-bit applications via IP, the Advantage Database Server creates two sockets and listens for specific multicast and mail (NetBIOS mailslot) packets. For IPX networks, the Advantage Database Server uses SAPs for discovery. Generally, a 6420 error is caused by a network device blocking these discovery packets or by a server not responding to the packet requests.

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Solution:
The following are possible solutions:

1. Advantage Database Server versions 6.11 and newer provide the ability to connect by specifying an IP address in the ADS.INI file. This direct connection method eliminates the discovery process and will resolves 6420 errors.

For a direct connection, configure the IP_PORT on the server in the ADS.CFG for Netware or in the Advantage Configuration Utility for Windows 2000/NT. Then, specify the IP address and port in the ADS.INI file.

ADS.INI example
[MYSERVER]
LAN_IP=155.690.41.69
LAN_PORT=2001

For further instructions, see LAN_IP/LAN_PORT in the Advantage help file. This functionality is not available for IPX connections.

2. Verify that the client can ping the server by IP address and by name (example: PING .) If this fails, install WINS, DNS or modify the workstation's LMHosts file.

3. A firewall may be eliminating Advantage UDP/IP packets. The firewall router logs will indicate the Advantage packets that are being filtered. See the Advantage help file for configuring the IP port for the Advantage Database Server, and then configure the firewall to allow UDP and IP packets through the configured port.

4. If the first connection fails with a 6420, but subsequent connections succeed, the client may not be receiving a response from the DNS, WINS, or LMHosts file for name resolution. An ARP (Address Request Protocol) request is sent out to get the address of the mailslot server. This ARP will go out on IPX or IP since it uses NetBios. If it goes out on IPX then the request gets handled. However, if IPX is not installed then IP is used. If a gateway does not have IP installed, ARPs sent to the gateway will not get a response. After several tries, a broadcast is sent and a response is received. Then the server is found and a connection is established. This can take up to 12 seconds under this scenario. For a limited time this address is kept for quick reference.

The problem is that the name of the Windows NT server machine is not being resolved to an IP address. Make sure either a DNS, WINS or LMHosts name resolution is in place.

5. A 6420 may be caused by a WSOCK32.DLL that is corrupt, that is non-Microsoft, or that is outdated (1994 or older). Update the WSOCK32.DLL by placing in the Windows\System directory or by placing it in the application directory.

6. 6420 (Unable to discover the Advantage Database Server) errors can occur after updating to v5.7 or newer client communications DLL. Earlier versions of the Advantage client communications layer DLL used an obsolete Microsoft API call that sometimes worked when the standard method of discovery of the Advantage Database Server failed. ADSCOM.TXT generated from a version 5.6 or older environment utility would show a call to OldGetRemoteAddress.

7. A client using a dial-up connection to a network and ADSDOSIP can get 1015 or 6420 errors on either Windows 95 or Windows NT if they started ADSDOSIP before initializing the dial-up connection. Initialize the dial-up connection before starting ADSDOSIP.

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