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Version: v9.0.x
warning

This document is relevant only for fungible token transfers over channels on v1 of the ICS-20 protocol.

Messages

MsgTransfer

A fungible token cross chain transfer is achieved by using the MsgTransfer:

type MsgTransfer struct {
SourcePort string
SourceChannel string
Token sdk.Coin
Sender string
Receiver string
TimeoutHeight ibcexported.Height
TimeoutTimestamp uint64
Memo string
}

This message is expected to fail if:

This message will send a fungible token to the counterparty chain represented by the counterparty Channel End connected to the Channel End with the identifiers SourcePort and SourceChannel.

The denomination provided for transfer should correspond to the same denomination represented on this chain. The prefixes will be added as necessary upon by the receiving chain.

If the Amount is set to the maximum value for a 256-bit unsigned integer (i.e. 2^256 - 1), then the whole balance of the corresponding denomination will be transferred. The helper function UnboundedSpendLimit in the types package of the transfer module provides the sentinel value that can be used.

Memo

The memo field was added to allow applications and users to attach metadata to transfer packets. The field is optional and may be left empty. When it is used to attach metadata for a particular middleware, the memo field should be represented as a json object where different middlewares use different json keys.

For example, the following memo field is used by the callbacks middleware to attach a source callback to a transfer packet:

{
"src_callback": {
"address": "callbackAddressString",
// optional
"gas_limit": "userDefinedGasLimitString",
}
}

You can find more information about other applications that use the memo field in the chain registry.