Start relaying

In the previous tutorial, you learned about how to relay packets between a pair of chains on a relay path. Now, you will learn how to relay packets on an arbitrary topology.

WARNING Before proceeding to the sections below, please first, make sure you followed the steps in the Build the topology section.

The chains should be fully connected and the relayer should be setup to relay on these channels:

flowchart TD 
ibc0((ibc-0))
ibc0ibc1[[channel-0]]
ibc0ibc3[[channel-2]]

ibc1((ibc-1))
ibc1ibc0[[channel-0]]
ibc1ibc2[[channel-1]]

ibc2((ibc-2))
ibc2ibc1[[channel-1]]
ibc2ibc3[[channel-2]]

ibc3((ibc-3))
ibc3ibc0[[channel-0]]
ibc3ibc2[[channel-2]]

ibc0---ibc0ibc1---ibc1ibc0---ibc1
ibc0---ibc0ibc3---ibc3ibc0---ibc3
ibc1---ibc1ibc2---ibc2ibc1---ibc2
ibc2---ibc2ibc3---ibc3ibc2---ibc3

Query balances

  • Balances on ibc-0:

    gaiad --node tcp://localhost:27050 query bank balances $(gaiad --home ~/.gm/ibc-0 keys --keyring-backend="test" show wallet -a)
    
  • Balances on ibc-1:

    gaiad --node tcp://localhost:27060 query bank balances $(gaiad --home ~/.gm/ibc-1 keys --keyring-backend="test" show wallet -a)
    
  • Balances on ibc-2:

    gaiad --node tcp://localhost:27070 query bank balances $(gaiad --home ~/.gm/ibc-2 keys --keyring-backend="test" show wallet -a)
    
  • Balances on ibc-3:

    gaiad --node tcp://localhost:27080 query bank balances $(gaiad --home ~/.gm/ibc-3 keys --keyring-backend="test" show wallet -a)
    

NOTE the RPC addresses used in the two commands above are configured in ~/.hermes/config.toml file. It can also be found with gm status

At this point in the tutorial, every command should output something similar to:

balances:
- amount: "100000000"
  denom: samoleans
- amount: "99982481"
  denom: stake
pagination:
  next_key: null
  total: "0"

Start relaying

Now, let's exchange samoleans between chains.

  • Open a new terminal and start Hermes using the start command :

    hermes start
    

    Hermes will first relay the pending packets that have not been relayed and then start passively relaying by listening for and acting on packet events.

  • Let's transfer 1000000 samoleans from ibc-1 to ibc-3. There is a direct path between ibc-1 (channel-2) and ibc-3 (channel-1). Let's attempt the transfer on this path.

    • In a separate terminal, use the ft-transfer command to send 1000000 samoleans from ibc-1 to ibc-3 from channel-2:
    hermes tx ft-transfer --timeout-seconds 10000 --dst-chain ibc-3 --src-chain ibc-1 --src-port transfer --src-channel channel-2 --amount 1000000
    
    • Wait a few seconds then query balances on ibc-1 and ibc-3. You should observe that ibc-1 lost 1000000 samoleans but ibc-3 did not receive any:

      • Balances at ibc-1 :
        balances:
        - amount: "99000000"
        denom: samoleans
        - amount: "99980646"
        denom: stake
        pagination:
        next_key: null
        total: "0"
        
      • Balances at ibc-3 :
        balances:
        - amount: "100000000"
        denom: samoleans
        - amount: "99979803"
        denom: stake
        pagination:
        next_key: null
        total: "0"
        
    • Observe the output on the relaying terminal and verify that no event is processed.

    If you correctly created the packet filters in the previous section, Hermes does not relay on this path. So what happened to the 1000000 samoleans you just sent ? It is stuck until a relayer decides to relay this packet to ibc-3. For now, let's forget about these samoleans. We can get as many as we want anyway.

    It might be impossible to send packets directly from ibc-1 to ibc-3, however, it is possible to use ibc-2 as a bridge:

graph LR;
    A((ibc-1)) --> B((ibc-2)) --> C((ibc-3))
  • In a separate terminal, use the ft-transfer command to send 1000000 samoleans from ibc-1 to ibc-2 from channel-1:

    hermes tx ft-transfer --timeout-seconds 10000 --dst-chain ibc-2 --src-chain ibc-1 --src-port transfer --src-channel channel-1 --amount 1000000
    
  • Wait a few seconds then query balances on ibc-1 and ibc-2. You should observe something similar to:

    • Balances on ibc-1:
      balances:
      - amount: "98000000"
      denom: samoleans
      - amount: "99979707"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      
    • Balances at ibc-2:
      balances:
      - amount: "1000000"
      denom: ibc/C1840BD16FCFA8F421DAA0DAAB08B9C323FC7685D0D7951DC37B3F9ECB08A199
      - amount: "100000000"
      denom: samoleans
      - amount: "99979154"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      

    The samoleans were transferred to ibc-1 and are visible under the denomination ibc/C1840... (it might be a different one for you).

  • Transfer these tokens to ibc-3:

    hermes tx ft-transfer --timeout-seconds 10000 --denom ibc/C1840BD16FCFA8F421DAA0DAAB08B9C323FC7685D0D7951DC37B3F9ECB08A199 --dst-chain ibc-3 --src-chain ibc-2 --src-port transfer --src-channel channel-2 --amount 1000000
    
  • Wait a few seconds then query balances on ibc-2 and ibc-3. You should observe something similar to:

    • Balances on ibc-2:
      balances:
      - amount: "0"
      denom: ibc/C1840BD16FCFA8F421DAA0DAAB08B9C323FC7685D0D7951DC37B3F9ECB08A199
      - amount: "100000000"
      denom: samoleans
      - amount: "99977059"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      
    • Balances on ibc-3:
      balances:
      - amount: "1000000"
      denom: ibc/C658F0EB9DE176E080B586D634004141239C3E55676462C976266DB54C56EBE4
      - amount: "100000000"
      denom: samoleans
      - amount: "99978251"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      

    The tokens were correctly received by ibc-3 under the denomination ibc/C658....

Send back the tokens

Now let's send some of these coins back to ibc-1. We will dedicate half of them to learn a valuable lesson while the other half will be correctly transferred back.

The wrong way

Let's start with a common mistake and send back these coins on a different path than the one they were received on:

Another path to ibc-1

graph LR;
A((ibc-3)) --> B((ibc-0)) --> C((ibc-1));
  • Use the ft-transfer command to transfer 500000 ibc/C658... tokens from ibc-3 to ibc-0:

    hermes tx ft-transfer --timeout-seconds 10000 --denom ibc/C658F0EB9DE176E080B586D634004141239C3E55676462C976266DB54C56EBE4 --dst-chain ibc-0 --src-chain ibc-3 --src-port transfer --src-channel channel-0 --amount 500000
    
  • Wait a few seconds, then query balances on ibc-0 and ibc-3. You should observe something similar to:

    • Balances on ibc-0:
      balances:
      - amount: "500000"
      denom: ibc/563FDAE5A0D8C15013E4485134A2D2EE3317452278B56B2ED63DDB4EB677DF84
      - amount: "100000000"
      denom: samoleans
      - amount: "99980928"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      
    • Balances on ibc-3:
      balances:
      - amount: "500000"
      denom: ibc/C658F0EB9DE176E080B586D634004141239C3E55676462C976266DB54C56EBE4
      - amount: "100000000"
      denom: samoleans
      - amount: "99976153"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      

    The tokens were correctly received by ibc-0 under the denomination ibc/563....

  • Transfer the ibc/563... tokens from ibc-0 to ibc-1:

    hermes tx ft-transfer --timeout-seconds 10000 --denom ibc/563FDAE5A0D8C15013E4485134A2D2EE3317452278B56B2ED63DDB4EB677DF84 --dst-chain ibc-1 --src-chain ibc-0 --src-port transfer --src-channel channel-0 --amount 500000
    
  • Wait a few seconds then query balances on ibc-0 and ibc-3. You should observe something similar to:

    • Balances on ibc-0:
      balances:
      - amount: "0"
      denom: ibc/563FDAE5A0D8C15013E4485134A2D2EE3317452278B56B2ED63DDB4EB677DF84
      - amount: "100000000"
      denom: samoleans
      - amount: "99978828"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      
    • Balances on ibc-1:
      balances:
      - amount: "500000"
      denom: ibc/8F3641F853A1D075C549E733AB624BA8607C8D2FFC26B32717DE660AE6A34A73
      - amount: "98000000"
      denom: samoleans
      - amount: "99978141"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      

    The tokens were successfully received by ibc-1 under the denomination ibc/8F3... while they should be recognized as samoleans. Indeed, it is impossible to transfer back tokens from a different channel than the one they were received from.

    Let's forget about these tokens.

The right way

Now that you have seen the wrong way to transfer back tokens, let's see the right way. Tokens should be transferred back on the same path they were received.

Correct Path:

graph LR;
A((ibc-3))-->B((ibc-2))-->C((ibc-1));
  • Use the ft-transfer command to transfer 500000 ibc/C658... tokens from ibc-3 to ibc-2:

    hermes tx ft-transfer --timeout-seconds 10000 --denom ibc/C658F0EB9DE176E080B586D634004141239C3E55676462C976266DB54C56EBE4 --dst-chain ibc-2 --src-chain ibc-3 --src-port transfer --src-channel channel-2 --amount 500000
    
  • Wait a few seconds then query balances on ibc-2 and ibc-3. You should observe something similar to:

    • Balances at ibc-2:
      balances:
      - amount: "500000"
      denom: ibc/C1840BD16FCFA8F421DAA0DAAB08B9C323FC7685D0D7951DC37B3F9ECB08A199
      - amount: "100000000"
      denom: samoleans
      - amount: "99975713"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      
    • Balances at ibc-3:
      balances:
      - amount: "0"
      denom: ibc/C658F0EB9DE176E080B586D634004141239C3E55676462C976266DB54C56EBE4
      - amount: "100000000"
      denom: samoleans
      - amount: "99973935"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      

    The tokens were correctly received by ibc-0 under the denomination ibc/C184.... The tokens retrieved the denomination they had before they were transferred to ibc-3.

  • Transfer the ibc/C184... tokens from ibc-2 to ibc-1:

    hermes tx ft-transfer --timeout-seconds 10000 --denom ibc/C1840BD16FCFA8F421DAA0DAAB08B9C323FC7685D0D7951DC37B3F9ECB08A199 --dst-chain ibc-1 --src-chain ibc-2 --src-port transfer --src-channel channel-1 --amount 500000
    
  • Wait a few seconds, then query balances on ibc-1 and ibc-2. You should observe something similar to:

    • Balances on ibc-1:
      balances:
      - amount: "500000"
      denom: ibc/8F3641F853A1D075C549E733AB624BA8607C8D2FFC26B32717DE660AE6A34A73
      - amount: "98500000"
      denom: samoleans
      - amount: "99975741"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      
    • Balances on ibc-2:
      balances:
      - amount: "0"
      denom: ibc/C1840BD16FCFA8F421DAA0DAAB08B9C323FC7685D0D7951DC37B3F9ECB08A199
      - amount: "100000000"
      denom: samoleans
      - amount: "99974602"
      denom: stake
      pagination:
      next_key: null
      total: "0"
      

    The tokens were successfully received by ibc-1 under the denomination samoleans.


Next Steps

In the next section, you will start new instances of Hermes to relay packets over the channels that were filtered out by the first instance.