beast/example/server-framework

HTTP and WebSocket built on Boost.Asio in C++11

Server-Framework

This example is a complete, multi-threaded server built with Beast. It contains the following components

• WebSocket ports (synchronous and asynchronous)

  • Echoes back any message received

• HTTP ports (synchronous and asynchronous)

  • Serves files from a configurable directory on GET request
  • Responds to HEAD requests with the appropriate result
  • Routes WebSocket Upgrade requests to a WebSocket port
  • Handles Expect: 100-continue
  • Supports pipelined requests

The server is designed to use modular components that users may simply copy into their own project to get started quickly. Two concepts are introduced:

PortHandler

The PortHandler concept defines an algorithm for handling incoming connections received on a listening socket. The example comes with four port handlers:

• http_sync_port Serves HTTP content using synchronous Beast calls

• http_async_port Serves HTTP content using asynchronous Beast calls

• ws_sync_port A synchronous WebSocket echo server using synchronous Beast calls

• ws_async_port An asynchronous WebSocket echo server using synchronous Beast calls

A port handler takes the stream object resulting form an incoming connection request and constructs a handler-specific connection object which provides the desired behavior.

Service

The HTTP ports which come with the example have a system built in which allows installation of framework and user-defined "HTTP services". These services inform connections using the port on how to handle specific requests. This is similar in concept to an "HTTP router" which is an element of most modern servers.

These HTTP services are represented by the Service concept, and managed in a container holding a type-list, called a service_list. Each HTTP port allows the sevice list to be defined at compile-time and initialized at run time. The framework provides these services:

• file_service Produces HTTP responses delivering files from a system path

• ws_upgrade_service Transports a connection requesting a WebSocket Upgrade to a websocket port handler.

Relationship

This diagram shows the relationship of the server object, to the four ports created in the example program, and the HTTP services contained by the HTTP ports: