Client

Core Idea

A client is the program that initiates a request to a server.

Course Examples

• ssh is a client for the SSH server.
• curl is a client for HTTP and other protocols.
• A browser is an HTTP client.
• git push uses a git client to talk to a git server.

Client Questions To Ask

• What server name or address am I contacting?
• What protocol am I using?
• What port is implied or explicit?
• What path, repository, or resource am I asking for?
• What authentication is required?
• What error did the client receive?

Example

curl -I https://lf2607.kolamayermakers.org/~username/

• Client: curl
• Protocol: HTTPS
• Server name: lf2607.kolamayermakers.org
• Path: /~username/
• Default port: 443

Common Confusions

• Client error messages are not always root causes; they are what the client could observe.
• A browser and curl can request the same URL but display different levels of detail.
• Authentication failure can be a client key problem, a server account problem, or a permission problem.
• Retrying without reading the error usually wastes time.

Proof Check

Choose one command from ssh, curl, or git push. Identify the client, server, protocol, and authentication method.

Docs Pointers

• Run man ssh, man curl, and git help push.
• Read Server for the process receiving the request.
• Read IP Networking for addresses, ports, and protocols.