This paper proposes a pluggable service-to-service (S2S) communication mechanism in a middleware for home networks, called Virtual Networked Appliance (VNA) architecture. In the architecture, service description method and the plug-gable S2S communication mechanism are separated in an orthogonal way. Through the separation, VNA architecture solved problems of home networks on which users have to operate multiple heterogeneous middleware technologies simultaneously: middleware fragmentation problem, due to complexity of realizing heterogeneous services on one middle-ware technology: aspect realization violation problem. The pluggable S2S communication mechanism provides service programmers with a simple aspect representation method to define a service-specific protocol concern apart from the service's implementation. It also provides off-the-shelf protocol modules of such well-known communication protocols as RTP, RTSP, HTTP, and SMTP for an inter-service communication, and dynamically loads them based on the aspects defined by the programmer. This reduces the complexity of implementing heterogeneous services on the VNA architecture, thereby addressing the problems. In this paper, we first clarify the two problems. Then, we describe the proposed mechanism with an overview of the middleware architecture referring to a composite service: "Follow-You-and-Me Video."