A bchd rpc client for browsers using grpc/grpc-web

This package provides a simple gRPC client for connecting web applications to a bchd full node.

A mobile friendly version of this project is formatted from markdown by github pages.

Getting Started

For a quick example usage subscribing transactions see the console here, or an experimental example using this module in a web worker.

Detailed RPC Documentation for the rpc protocol is a work in progress.

Client Documentation detailing methods and utility functions.

Mocha browser tests should provide some working examples.

This is slightly more than a stock client generated from protocol buffers. The following utilities have been added:

• Simple utilities to transform hex/base64/Uint8Arrays without nodejs Buffer
• A function to transform a number to a little-endian array
• Functions to validate a merkle proof from bchd
• A class to read and match compact filters for outpoints and public keys

For Bitcoin Cash and bchd specifically, functions are currently here to validate a transaction and block, as well as other utilities to handle different data types used or sent by bchd.

Motivation

This project uses Google's grpc/grpc-web library to generate a client, rather than the older and more widely used @improbable-eng/grpc-web.

The client is built from the pb files in advance rather than on-the-fly, a functionality which may be employed with the @improbable library.

The motivation is toward lower maintenance, long-term stability and support by using the google library, not that this thinking played out well with the framework formerly known as angular.

One notable limitation of the official grpc/grpc-web library is a lack of FETCH support.

See also

• The official documentation for bchrpc.
• The reference implementation from the bchd team.
• Notes on the limitations of multiplexing from a browser

Alternative implementations of this project are built using the improbable-eng library here:

• For the web: grpc-bchrpc-web
• Using a local bchd node from nodejs: grpc-bchrpc-node

Scripts

Note: this project was created in node v12.2.0 (LTS) and used protoc version 3.11.4; and is open to using features from es2017 although initially targeted at es6.

Build

To build:

npm run build        # transpile typescript, browserify and minify use
npm run build:docs   # build documentation for the client class

Running Tests

Tests can be run either from console or in a browser. The typescript is loaded via ts-node, in that context.

npm run test          # run tests in node
npm run test:browser  # run tests in a browser

Updating the Spec

If for some reason you need to update the gcash proto files yourself to add some future functionality use:

npm run pb-clean     # remove old definitions
npm run pb-update    # download bchrpc.proto from gcash/bchd/master
npm run pb-build     # create client library
npm run pb-doc       # generate documentation

Important: an installed version of protoc
is required to run pb-build.

IN ADDITION you must have protoc-gen-grpc-web, see grpc-web

Using bchrpc in a Postman-like webgui

To facilitate debugging and development of the client, it may be useful make calls using a webui. The following npm scripts are provided, assuming you have golang installed.

npm run pb-grpcui-install     # install grpcui
npm run pb-grpcui             # run a local webui against a bchd node

BCHD Full Nodes w/ gRPC

Mainnet:

• https://bchd.greyh.at:8335
• https://bchd.imaginary.cash:8335
• https://bchd.fountainhead.cash:443
• https://bchd.sploit.cash:443

Testnet:

• https://bchd.greyh.at:18335
• https://bchd-testnet.greyh.at:18335