What are the differences between –rpc and –http in Ethereum?

In Ethereum clients like Geth, both the --rpc and --http flags serve similar purposes, as they both enable the JSON-RPC interface. However, they differ in the transport protocol used for communication and the way the interface is accessed.

1. –rpc (RPC over HTTP and/or WebSockets):
   • When you use the --rpc flag, you are enabling the JSON-RPC interface to accept requests over both HTTP and WebSocket protocols.
   • This means that the Ethereum node will listen on a specified port (usually 8545 by default) for both HTTP and WebSocket connections.
   • You can send JSON-RPC requests using either HTTP POST or WebSocket connections to interact with the Ethereum node.
   • This option gives you flexibility in choosing either HTTP or WebSocket communication based on your application’s requirements.
2. –http (RPC over HTTP):
   • When you use the --http flag, you are specifically enabling the JSON-RPC interface over the HTTP protocol.
   • The Ethereum node will listen on a specified port (usually 8545 by default) for incoming HTTP POST requests only.
   • You can send JSON-RPC requests using HTTP POST to interact with the Ethereum node.
   • This option limits communication to HTTP and does not provide WebSocket support.

In summary, the primary difference between --rpc and --http is the transport protocols they support. --rpc enables both HTTP and WebSocket communication, while --http enables only HTTP communication. If you need the flexibility to use either HTTP or WebSocket for your JSON-RPC interactions, you should use the --rpc flag. If you only need to communicate over HTTP, the --http flag is sufficient.

For example, to enable the JSON-RPC interface over both HTTP and WebSocket, you can use the --rpc flag: