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SAP Sybase SQL Anywhere 16.0 » SQL Anywhere Server - Database Administration » SQL Anywhere database connections » Database connections » Troubleshooting: connections

 

Troubleshooting: How the Broadcast Repeater utility locates database servers

The Broadcast Repeater utility (dbns16) allows clients to find database servers running on other subnets and through firewalls where UDP broadcasts normally do not reach, without using the Host connection parameter or LDAP.

Prérequis

There are no prerequisites for this task.

Contexte et remarques

Any number of DBNS processes can communicate with each other. Each DBNS process connects to every other DBNS that it is aware of, and the different DBNS processes share their lists of DBNS processes. For example, suppose you start two DBNS processes, A and B. If you start a third DBNS process, C, in a third subnet, passing the address of B to C, then B tells C about A, and C then connects to A.

Note

Running more than one DBNS process in a single subnet is generally not necessary, and is not recommended.

If you must run multiple DBNS processes in a single subnet, then you must specify a different port for each DBNS process. A single DBNS process can only listen on one port. Use the -ap parameter in the Broadcast Repeater utility (dbns16).

If either the Host connection parameter or the HOST protocol option is used, then the Broadcast Repeater utility is not needed.

 Task
  1. Start a DBNS (database name service) process on any computer in a subnet.

  2. Start a DBNS process on any computer in a different subnet and pass the computer name or IP address of the first computer as a parameter.

    The two DBNS processes make a TCP/IP connection to each other.

  3. The DBNS processes now listen for broadcasts on each of their own subnets. Each DBNS process forwards requests over the TCP/IP connection to the other DBNS process, which re-broadcasts the requests on its subnets and also forwards responses back to the originating DBNS process, which sends them to the original client.

Résultat

Regular SQL Anywhere broadcasts on either of the subnets reach database servers on the remote subnet, and clients are able to connect to database servers on the remote subnet without specifying the HOST parameter.

 See also