Tip: Sending and Receiving a Packet

In KENS, there are sendPacket and packetArrived methods to send and receive packets. There is a packetArrived method in TCPAssignment.cpp.

void TCPAssignment::packetArrived(std::string fromModule, Packet &&packet) {
  // Remove below
  (void)fromModule;
  (void)packet;
}

Every correct formed packet is transferred to this method. You can extract data from the received packet via Packet interfaces. For example, you can read its raw data from 0 to 16 by calling readData method. Note that after handling the received packet, you may have to return a blocked system call as described in a previous section.

Sending a packet uses the sendPacket method. It receives a packet object to send and transfers it to the next module. In KENS, "IPv4" is the only next module, so you can safely set the toModule parameter to "IPv4".

We strongly recommend you to use R-value for sending packets. This prevents reuse of sent packets and their UUIDs.

sendPacket("IPv4", packet);              // OK, but not recommended
sendPacket("IPv4", std::move(packet));   // Recommended

You can create a new packet from scratch or by cloning an existing packet object. The cloning creates a new packet which has the same data with origin but not UUID. Note that copying (using = operator) just creates a new packet object which has the same data and UUID.

// Creating a new packet from scratch

size_t packet_size = 100;
Packet pkt (packet_size);
pkt.writeData(0, data, 20);

...


// Cloning an existing packet

Packet pkt2 = pkt.clone();  // cloning pkt. pkt2 has different UUID
Packet pkt3 = pkt;          // copying pkt. pkt3 has same UUID