Unidirectional Channel

A unidirectional channel (also called a one-way channel) is a payment channel where funds can only flow in a single direction: from the channel initiator to the acceptor. Unlike a standard bidirectional channel, the acceptor cannot send payments back through the channel.

When to Use a Unidirectional Channel

Unidirectional channels are useful in scenarios where:

• One-way streaming payments: A subscriber pays a content provider continuously, but never expects refunds or payments back
• Merchant-only receiving: A merchant opens a channel solely to receive customer payments
• Simplified channel management: No need to worry about balanced liquidity in both directions

How It Works

In a unidirectional channel:

1. The initiator opens the channel and provides all the funding
2. The acceptor does not contribute any funds to the channel
3. The initiator can send payments to the acceptor through off-chain TLC updates
4. The acceptor cannot send payments back to the initiator through this channel
5. When the channel closes, the final balance is settled on-chain

Opening a Unidirectional Channel

Set one_way: true when calling open_channel:

{
  "jsonrpc": "2.0",
  "method": "open_channel",
  "params": [
    {
      "peer_id": "QmbLM...",
      "funding_amount": "0x77359400",
      "one_way": true
    }
  ],
  "id": 1
}

Or using fnn-cli:

fnn-cli channel open_channel --peer-id QmbLM... --funding-amount 49900000000 --one-way

Channel Properties

Monitoring

When listing channels, check is_one_way to verify the channel type:

fnn-cli channel list_channels

The response will include:

{
  "channel_id": "0x...",
  "is_one_way": true,
  "state": { "state_name": "ChannelReady" }
}

Related Topics

• Channel Lifecycle — full channel state transitions
• Channel Rebalancing — adjust liquidity in bidirectional channels
• Payment Lifecycle — how payments are processed