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BTP Service Handler (BSH)

Introduction

BTP Service Handler (BSH) may send messages through BTP Message Center(BMC) from any user request. Of course, the request may come from other smart contracts. It also have responsibility to handle the message from other BSHs. BSH can communicate other BSHs with same service name. If there is already the service using same name, then it should choose other name for the service when it registers a new service.

The BTS contract is a BSH contract, which originates cross chain token transfer and gets response back from BTS of destination chain and services based on the response received. BTS contract maintains information about blacklist and token transfer limit as well.

BTS, being a BSH, needs to be registered to the BMC, before being able to send a BTP Message or handle incoming response messages.

For a contract to be BSH, the following are required:

  1. Implement BSH interface.
  2. Registered to the BMC through BMC.addService

After the registration, it may send messages through BMC.sendMessage.

If there is an error while it delivers the message, then it will return error information though handleBTPError.

If it's successfully delivered, then BMC will call handleBTPMessage of the target BTS.

While it processes the message, it may reply though BMC.sendMessage.

Setup

  1. Registers BSH for the services in BMC. (BSH should be deployed before the registration)
  2. Add links, BMCs of directly connected blockchains
  3. Add routes to other BMCs of in-directly connected blockchains

BSH Interface

The BTP Service Handler (BSH) should implement the following 3 methods:

  • handleBTPMessage

    • Method

      • handleBTPMessage

    • Parameters

      Parameters Type Info
      _from string An originated network address of a request
      _svc string Service name of BSH contract
      _sn integer Serial number of a service request
      _msg bytes RLP message of a service request/service response

    • Implementation

  • handleBTPError

    • Method

      • handleBTPError

    • Parameters

      Parameters Type Info
      _src string An originated network address of a request
      _svc string Service name of BSH contract
      _sn integer Serial number of a service request
      _code integer Response code of a message (RC_OK / RC_ERR)
      _msg string Response message

    • Implementation

  • handleFeeGathering

    • Method

      • handleFeeGathering

    • Parameters

      Parameters Type Info
      _fa string BTP Address of fee aggregator
      _svc string Service name of BSH contract

    • Implementation