The GDB User Guide [3] documents the Remote Serial Protocol (RSP) for communicating with remote targets. The target must act as a server for the RSP, and the source distribution includes stub implementations for architectures such as the Motorola 680xx and Sun SPARC. The User Guide offers advice on how these stubs can be modified and integrated for new targets.

However the examples have not been changed for several years, and the advice on using the stubs is now out of date. The documentation also lacks any explanation of the dynamics of the protocol—the sequence of commands/responses used to effect the various GDB commands.

This document aims to fill that gap, by explaining how the RSP works today and how it can be used to write a server for a target to be debugged with GDB.

Throughout, examples are provided from the author's experience implementing a RSP server for the OpenRISC 1000 architecture. This document captures the learning experience, with the intention of helping others.