An apparatus, method, program product, and system are disclosed for seamless connection handshake for a reliable multicast session. A node module detects a new node attempting to join a multicast networking session. A handshake module generates a control packet comprising session initiation data for the new node. A packet module creates a combined data packet comprising the control packet and the multicast data packet and sends the combined data packet to the new node. The node module joins the new node to the ongoing multicast networking session without disturbing ongoing data transmissions during the multicast networking session.