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Version: v4.6.x

IBC Applications


Learn how to build custom IBC application modules that enable packets to be sent to and received from other IBC-enabled chains.

This document serves as a guide for developers who want to write their own Inter-blockchain Communication Protocol (IBC) applications for custom use cases.

Due to the modular design of the IBC protocol, IBC application developers do not need to concern themselves with the low-level details of clients, connections, and proof verification. Nevertheless, an overview of these low-level concepts can be found in the Overview section. The document goes into detail on the abstraction layer most relevant for application developers (channels and ports), and describes how to define your own custom packets, IBCModule callbacks and more to make an application module IBC ready.

To have your module interact over IBC you must:

  • implement the IBCModule interface, i.e.:
    • channel (opening) handshake callbacks
    • channel closing handshake callbacks
    • packet callbacks
  • bind to a port(s)
  • add keeper methods
  • define your own packet data and acknowledgement structs as well as how to encode/decode them
  • add a route to the IBC router

The following sections provide a more detailed explanation of how to write an IBC application module correctly corresponding to the listed steps.


Working example

For a real working example of an IBC application, you can look through the ibc-transfer module which implements everything discussed in this section.

Here are the useful parts of the module to look at:

Binding to transfer port

Sending transfer packets

Implementing IBC callbacks