The network

import net adds endpoints that are transports. They are read and written by source, tap, target and sink like any other endpoint, and constructing one sends nothing. Naming the module in the program's first lines is how a program states that it may reach the network.

http(url) is Replayable: reading it sends one GET per evaluation and decodes the response body, so source gives a Seq:

import net
source(http("https://api.example.com/birds"), Json)

Seq<Data>

websocket(url) is live: each message is one document, read as it arrives, so reading it gives a Stream:

import net
tap(websocket("wss://events.example.com"), Json)

Stream<Data>

Writing an http endpoint sends one request per document, with the document as its body, by the method given, "GET" unless written. The response is read only for its status, and a status that is not a success is an evaluation failure naming the URL:

import net
source(file("examples/io/sightings.jsonl"))
| target(http("https://api.example.com/report", method = "POST"), Json)

Unit

socket(host, port) is a TCP connection: its documents are separated as their format separates them, one JSON value after another or one line at a time.

Without the import the endpoint constructors are not in scope:

source(http("https://api.example.com/birds"), Json)

check error[unknown-name]: `http` is provided by the `net` extension: write `import net`
 --> <expression>:1:8
  |
1 | source(http("https://api.example.com/birds"), Json)
  |        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

A header is ordinary data in the program's text, so a request that needs credentials belongs in configuration, as a source by id, and not in a program (sources and targets by id). A document being rendered reaches no network (effects and what a host allows).