20.4.2 Tcl APIs for the ping application

An example script for the ping application is under tcl/ex/diffusion3/simple-diffusion.tcl. The example scenario consists of 3 nodes of which one is a ping-sender and another is a ping-receiver. The source and sink nodes are far away from one another and communicate only through a third node. The option adhocRouting is defined as Directed_Diffusion. This enables a core-diffusion agent to be created during the time of node creation. Also it creates a diffusionApplication agent if one is not present already. And a gradient filter is attached by default to each diffusion-enabled node.

The ping sender application is created in the following way:

set src_(0) [new Application/DiffApp/PingSender]
$ns_ attach-diffapp $node_(0) $src_(0)
$ns_ at 0.123 "$src_(0) publish"

The first line creates a ping-sender object. Simulator class method attach-diffapp basically attaches the application to the underlying diffusionApplication agent for that given node. The command publish essentially ``starts'' the sender application.

Similarly the ping sink is created as follows:

#Diffusion sink application
set snk_(0) [new Application/DiffApp/PingReceiver]
$ns_ attach-diffapp $node_(2) $snk_(0)
$ns_ at 1.456 "$snk_(0) subscribe"

The command subscribe once again starts the ping-receiver application.

Thus in order to create your own application, you need to :

1.

define attribute-factories and attributes for application interest/data.

2.

create the application class (using dr-library APIs)

3.

add tcl commands to start the application

See tcl/lib/ns-lib.tcl, ns-diffusion.tcl for implementations of OTcl hooks for directed diffusion. Alo see chapter on Mobility in this manual for details on mobility model and wireless simulations in .