Same details on DIM Configuration
(private networks, machines with multiple network interfaces, etc.)

Setting Up DIM Processes

A few environment variables can be used to configure DIM processes:

• DIM_DNS_NODE
  Before starting a Server or a Client to tell them where the DNS is running.
• DIM_DNS_PORT
  Before starting the DNS, a Server or a Client if the default DNS port number (2505) is not to be used.
  For example in order to be able to run two DNSs in the same machine.
• DIM_HOST_NODE
  Before starting a Server, to specify which IP name/IP address should be used by clients to connect to this server
  (if the default host interface* is not to be used).
  It can be the IP name (ex.: pclhcb155.cern.ch) or the IP address (ex.: 137.138.214.208)
  * The default host interface can be retrieved with the command line command: hostname
  • Note: The DIM Name Server (DNS) is also a Server (DIS_DNS) for replying to DID and for answering DimBrowser requests.
    So DIM_HOST_NODE can also be set for the DNS in order to choose on which interface it should answer.

 Some DIM functions can also be used to dynamically Set Up DIM Processes:

• For a DIM Client:
  • dic_set_dns_node(), dic_set_dns_port(), etc. and the C++ equivalents: DimClient::setDnsNode(), etc.
• For a DIM Server:
  • dis_set_dns_node(), dis_set_dns_port(), etc. and the C++ equivalents: DimServer::setDnsNode(), etc.

  These functions can be used to independently specify which DNS to use for Servers and Clients even if both parts are running in the same process (but need to use different DNSs).

  Note: The "obsolescent" functions dim_set_dns_node(), dim_set_dns_port(), etc. specify the same DNS for a complete process (so for both client and server part if running in the same process).

Using DIM across different Networks

In a node with two Ethernet interfaces (or in general visible on two networks):

• The DNS will answer to servers and client on both networks. Only its server part - DIS_DNS (the one that answers to DID and DimBrowser requests) would in principle answer only to one of the networks (either the default interface* or the one specified via "DIM_HOST_NODE").
• But, in fact, if the DNS or any server is started with the environment variable DIM_HOST_NODE set to the interface that is not the default* one. Than both the DNS (including the server part) and any DIM servers running on this dual interface machine will be accessible from both networks. For example DID will work fine on both networks.
  * The command "hostname" returns the name of the default network interface.

Note: Although the DNS may respond to all servers and clients on both networks, of course clients on one network will not be able to connect to servers which have a single interface on a different network.

A program: DimBridge is available, as an example, to transfer DIM services and commands from one DNS to another. (Supposing that the two DNSs are on different networks). Please note that such a Bridge should be used with care as it could create a bottleneck, since all services and commands have to be "tunneled" via it.
    Usage: DimBridge [from_node] to_node services
        from_node - by default DIM_DNS_NODE
        to_node - the complete node name of the new DNS
        services - the list of service names (wildcards allowed)

The user can also create its own client/server program that is a client on one interface and a server on the other one, using the same DNS, but then the user has to guarantee that the Service names published by the Server part are different from the ones already available. (DIM does not allow multiple services with the same name using the same DNS). 

Port Numbers used by DIM

When setting up (private) networks and gateways you may need to know the port numbers used by DIM for example to configure Firewalls.

• The DNS responds by default on port 2505 (although this can be changed by the variable DIM_DNS_PORT).
• DIM Servers (including DIS_DNS the server part of the DNS) will use ports in the range 5100 to 6000. A DIM server on one PC will take the first free port in this range, a second server on the same PC will take the next free port, etc.