react-native/docs/Network.md

id	title	layout	category	permalink	next
network	Network	docs	Polyfills	docs/network.html	timers

One of React Native's goals is to be a playground where we can experiment with different architectures and crazy ideas. Since browsers are not flexible enough, we had no choice but to reimplement the entire stack. In the places that we did not intend to change anything, we tried to be as faithful as possible to the browser APIs. The networking stack is a great example.

XMLHttpRequest

XMLHttpRequest API is implemented on-top of iOS networking apis. The notable difference from web is the security model: you can read from arbitrary websites on the internet since there is no concept of CORS.

var request = new XMLHttpRequest();
request.onreadystatechange = (e) => {
  if (request.readyState !== 4) {
    return;
  }

  if (request.status === 200) {
    console.log('success', request.responseText);
  } else {
    console.warn('error');
  }
};

request.open('GET', 'https://mywebsite.com/endpoint.php');
request.send();

Please follow the MDN Documentation for a complete description of the API.

As a developer, you're probably not going to use XMLHttpRequest directly as its API is very tedious to work with. But the fact that it is implemented and compatible with the browser API gives you the ability to use third-party libraries such as Parse or super-agent directly from npm.

Fetch

fetch is a better networking API being worked on by the standard committee and is already available in Chrome. It is available in React Native by default.

fetch('https://mywebsite.com/endpoint.php')
  .then((response) => response.text())
  .then((responseText) => {
    console.log(responseText);
  })
  .catch((error) => {
    console.warn(error);
  });

WebSocket

WebSocket is a protocol providing full-duplex communication channels over a single TCP connection.

var ws = new WebSocket('ws://host.com/path');

ws.on('open', function() {
  // connection opened
  ws.send('something');
});

ws.on('message', function(e) {
  // a message was received
  console.log(e.data);
});

ws.on('error', function(e) {
  // an error occurred
  console.log(e.message);
});

ws.on('close', function(e) {
  // connection closed
  console.log(e.code, e.reason);
});