Overview

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Overview

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Synopsis

Learn about the 09-localhost light client module. The 09-localhost light client module implements a stateless localhost loopback client with the ability to send and receive IBC packets to and from the same state machine.

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Context

In a multichain environment, application developers will be used to developing cross-chain applications through IBC. From their point of view, whether or not they are interacting with multiple modules on the same chain or on different chains should not matter. The localhost client module enables a unified interface to interact with different applications on a single chain, using the familiar IBC application layer semantics.

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Implementation

There exists a localhost light client module which can be invoked with the client identifier 09-localhost. The light client is stateless, so the ClientState is constructed on demand when required. To supplement this, a sentinel ConnectionEnd is stored in core IBC state with the connection identifier connection-localhost. This enables IBC applications to create channels directly on top of the sentinel connection which leverage the 09-localhost loopback functionality. State verification for channel state in handshakes or processing packets is reduced in complexity, the 09-localhost client can simply compare bytes stored under the standardized key paths.

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Localhost vs regular client

The localhost client aims to provide a unified approach to interacting with applications on a single chain, as the IBC application layer provides for cross-chain interactions. To achieve this unified interface though, there are a number of differences under the hood compared to a ‘regular’ IBC client (excluding 06-solomachine and 09-localhost itself). The table below lists some important differences: