# How to Create HTTP Servers

# Getting Started

A common use-case for a plugin is that you process some data from within core and want to make use of that data with an external application. The easiest way to do this is through an HTTP server that exposes an API from which you request the data.

Core provides a package called core-http-utils which provides everything you will need to run an HTTP server with plugins. Core uses hapi for all its HTTP based services as it enables developers to focus on writing reusable application logic instead of spending time building infrastructure.

# Installing Dependencies

As you've learned in How to write a Core Plugin you will need to install the required dependencies. For the example we will use we need core-http-utils which you can install with lerna add @swipechain/core-http-utils --scope=@vendor/demo-plugin.

# Creating Our Server

Now that core-http-utils is installed we can get started with starting our HTTP server, which is fairly simple.

import { createServer, mountServer } from "@swipechain/core-http-utils";

export async function startServer(config) {
  const server = await createServer({
    host: config.host,
    port: config.port
  });

  server.route({
    method: "GET",
    path: "/",
    handler(request, h) {
      return "Hello World";
    }
  });

  return mountServer("My HTTP Server", server);
}

startServer({ host: "localhost", port: 8000 });

This example will register a server with a single endpoint at http://localhost:8000/ where localhost is the host and 8000 the port. When you run curl http://localhost:8000/ you should get Hello World as response.

# Writing Tests for Your Server

Now that you have your HTTP server up and running it is time to write tests for it to guarantee that it returns the data you expect it to.

Core makes use of jest to write and execute tests and hapi.js request injection for testing all hapi based plugins. This allows us to send the requests directly to hapi rather then having to send a real request with something like axios.

import { startServer } from "./src/server";

let server;
beforeAll(async () => {
  server = await startServer({ host: "localhost", port: 8000 });
});

afterAll(async () => {
  await server.stop();
});

test("responds with 'Hello World' if '/' is hit", async () => {
  const { result } = await server.inject("/");

  expect(result).toBe("Hello World");
});

This test will do 3 things, lets break them down:

1. beforeAll will start a new instance of your server
2. test will inject a request to the / endpoint to your hapi server and expect the response body to be Hello World
3. afterAll will stop the instance that beforeAll created after all tests have finished

# Conclusion

This guide should give you a basic idea of how to create your own plugins that require a HTTP server with hapi, so head over to their tutorials or API documentation if you want to dig deeper and learn how it all works to build feature-rich plugins.