RMI回调-在线协议是什么？

Question

What is the "on the wire", TCP/IP level protocol when Java RMI is used with client callbacks?

Specifically, does the server initiate a separate TCP/IP connection to the client to make the callback, or is an existing TCP/IP connection used?

This reference: https://www.cis.upenn.edu/~bcpierce/courses/629/jdkdocs/guide/rmi/spec/rmi-protocol.doc.html indicates a HTTP POST is encapsulated in RMI to invoke the method, is the HTTP POST made by the server to the client for a callback?

Answer 1

What is the "on the wire", TCP/IP level protocol when Java RMI is used with client callbacks?

JRMP: Java Remote Method Protocol, unless you're using RMI/IIOP or JBoss or JERI or something else with a different RMI wire protocol.

Specifically, does the server initiate a separate TCP/IP connection to the client to make the callback

Yes.

or is an existing TCP/IP connection used?

No.

This reference: https://www.cis.upenn.edu/~bcpierce/courses/629/jdkdocs/guide/rmi/spec/rmi-protocol.doc.html indicates a HTTP POST is encapsulated in RMI to invoke the method, is the HTTP POST made by the server to the client for a callback?

Your link is an extremely ancient copy (1997) of the RMI Specification. The current version, dated 2010 , is available directly at Oracle. What it actually indicates is that it uses HTTP POST 'when circumstances warrant', ie as a fallback strategy if a direct TCP connection fails, and that only works if the RMI-CGI servlet is installed at the target.

RMI has no internal distinction between RMI calls and callbacks, so whether or not HTTP tunnelling is used is irrelevant to whether it's a callback or not, and vice versa.