The RSP packet interface is responsible for establishing the TCP/IP connection to and from the GDB server class, GdbServerSC and transferring RSP packets to and from the server. Packets are represented by their own class, RspPacket.

The class diagram in Figure 4.3 shows the relationship between these components.

Figure 4.3.  Class Diagram for the RSP interface.

The main GdbServerSC class is responsible for creating both the RspConnection instance and the RspPacket instance. In the RSP protocol there is only ever one packet active at any time, so a single instance suffices. It is passed by pointer to RspConnection for use when getting and putting packets on the TCP/IP connection.

The RSP connection is written in plain C++. There is no need for SystemC functionality. Indeed the use of system library routines to establish sockets and listen for new connections does not sit comfortably within the SystemC paradigm. A wait in the system library context suspends the entire process pending action, whereas wait in the SystemC context merely suspends the current thread.

This does not cause any practical problem with the synchronous GDB RSP interface. The TCP/IP connection is only used when the target is suspended, so there is no need for SystemC to be active.