20.5.1 Ping Application as implemented in C++

The ping-sender and -receiver classes, namely PingSenderApp and PingReceiverApp both derive from DiffApp, the parent class for all diffusion based applications. See diffusion3/lib/diffapp{.cc,.hh} for detailed implementation of the DiffApp class.

The ping-sender uses MySenderReceive object that handles all callbacks for it. Also the ping-sender defines two functions setupSubscription() and setupPublication(). The first function creates interest attributes that matches with data attributes it (the sender) has to offer. Next it calls the dr-library function subscribe(). The subscription is used by the ping-sender to create an internal state against which attributes for interests received from the network are matched against. Incase of a match, the matching data is sent outinto the network. Function setupPublication() create attributes for the data it has to offer and calls the library function publish() which inturn returns a publish handle. The ping-sender uses this handle to periodically send out data which is forwarded by the gradient to core-diffusion to be sent out into the network only if it finds a matching interest.

The ping-receiver object uses a similar callback object called MyReceiverReceive. And it defines a function setupSubscription() that creates attributes for the interest the receiver will be sending. Next it calls the dr library supported subscribe() which sends the interest out into the network. The recv() function is used to recv matching data and the receiver then calculates the latency for each data packet received from the ping-sender. The ping sender can be found under ping_sender.cc,.h. And the ping_receiver is implemented under ping_receiver.cc,.h. Some common defines and attribute factories for data/interest attributes are defined in ping.hh and ping_common.cc.