Understanding the Differences Between RPC and HTTP Services

Many developers are unclear about the difference between RPC (Remote Procedure Call) and HTTP calls; this article clarifies that RPC is typically built on TCP/IP while HTTP services operate on the HTTP protocol.

Before comparing RPC and HTTP, it reviews the OSI seven‑layer model (application, presentation, session, transport, network, data link, physical), noting that in practice the presentation and session layers are often merged with the application layer.

The focus then shifts to the application and transport layers, emphasizing that HTTP is an application‑layer protocol and TCP resides in the transport layer.

RPC architecture consists of four core components: Client, Server, Client Stub, and Server Stub. The client initiates requests, the server provides services, the client stub packages requests and sends them over the network, and the server stub unpacks the messages and invokes local methods.

RPC is commonly used in large enterprises where efficiency is critical; projects typically use Maven for dependency management, defining service interfaces in Java, packaging them as JARs, and sharing them between client and server.

Synchronous calls block the client until a response is received, while asynchronous calls allow the client to continue processing and receive results via callbacks or futures, similar to Java's Callable and Runnable interfaces.

Popular open‑source RPC frameworks include:

gRPC – Google’s framework based on HTTP/2, supporting multiple languages.

Thrift – Facebook’s cross‑language service framework with an IDL code generator.

Dubbo – Alibaba’s widely used Java RPC framework with pluggable protocols and serialization.

HTTP services are typically implemented as RESTful APIs, using standard HTTP methods (e.g., POST http://www.httpexample.com/restful/buyer/info/shar ) and returning JSON or XML. They are simple and fast for small‑scale integrations but involve more handshake overhead compared to long‑living RPC connections.

In large‑scale systems, RPC offers advantages such as persistent connections, reduced network overhead, built‑in service registries, and unified monitoring, whereas HTTP excels in rapid development and ease of use for fewer interfaces.

The article concludes that the choice between RPC and HTTP should be based on a thorough evaluation of project requirements rather than merely following trends.