To develop the applications for Internet appliances, embedded software development tools need various host tools such as cross compilers and binary utilities as well as a remote debugger, an interactive shell, and real time resource monitors. The heavy host-target communication overhead and inconsistency caused by various host tools make target monitor programs more complex. The authors propose a debugging protocol for these tools that supports several host-resident tools under the existence of RTOS. To abstract the details of the target systems, we have developed a target agent running as a task on the RTOS. The target agent is the counterpart of the host agent that supports host tools through communication over UDP/IP. The proposed architecture is implemented and tested on Esto (Embedded Systems Toolset), a development tool for Internet based embedded applications.