Connecting Across a Firewall

There are restrictions on connections when the client application is on one side of a firewall and the server is on the other. Firewall software filters network packets according to network port. Also, it is common to disallow UDP packets from crossing the firewall.

• Set the ClientPort parameter to a range of allowed values for the client application to use. You can then configure your firewall to allow these packets across. You can use the short form CPort.

• Set the HOST parameter to the host name on which the database server is running. You can use the short form IP.

• Specify the port your database server is using in the ServerPort parameter if it is not using the default port of 2638. You can use the short form Port.

• Set the DoBroadcast=NONE parameter to prevent UDP from being used when connecting to the server.

In this example, the connection string fragment:

• Restricts the client application to ports 5050 through 5060

• Connects to a server named myeng running on the machine at address myhost using the server port 2020

No UDP broadcast is carried out because of the DoBroadcast option.

CEng=myeng;Links=tcpip(ClientPort=5050–
5060;Host=myhost;Port=2020;DoBroadcast=NONE)