# Connecting nodes

Connect nodes through Receptor backends. TCP, UDP, and websockets are currently supported. For example, you can connect one Receptor node to another using the `tcp-peers` and `tcp-listeners` configuration options. Similarly you can connect Receptor nodes using the `ws-peers` and `ws-listeners` configuration options.

foo.yml

    ---
    version: 2
    node:
      id: foo

    log-level:
      level: Debug

    tcp-listeners:
      - port: 2222

bar.yml

    ---
    version: 2
    node:
      id: bar

    log-level:
      level: Debug

    tcp-peers:
      - address: localhost:2222

fish.yml

    ---
    version: 2
    node:
      id: fish

    log-level:
      level: Debug

    tcp-peers:
      - address: localhost:2222

If we start the backends for each of these configurations, this will form a three-node mesh. Notice bar and fish are not directly connected to each other. However, the mesh allows traffic from bar to pass through foo to reach fish, as if bar and fish were directly connected.

From three terminals we can start this example by using the container we provide on quay.io

    podman run -it --rm --network host --name foo -v${PWD}/foo.yml:/etc/receptor/receptor.conf quay.io/ansible/receptor

    podman run -it --rm --network host --name bar -v${PWD}/bar.yml:/etc/receptor/receptor.conf quay.io/ansible/receptor

    podman run -it --rm --network host --name fish -v${PWD}/fish.yml:/etc/receptor/receptor.conf quay.io/ansible/receptor

Logs from fish shows a successful connection to bar via foo.

    INFO 2021/07/22 23:04:31 Known Connections:
    INFO 2021/07/22 23:04:31    fish: foo(1.00)
    INFO 2021/07/22 23:04:31    foo: bar(1.00) fish(1.00)
    INFO 2021/07/22 23:04:31    bar: foo(1.00)
    INFO 2021/07/22 23:04:31 Routing Table:
    INFO 2021/07/22 23:04:31    foo via foo
    INFO 2021/07/22 23:04:31    bar via foo

## Configuring backends

`redial` If set to true, receptor will automatically attempt to redial and restore connections that are lost.

`cost` User-defined metric that will be used by the mesh routing algorithm. If the mesh were represented by a graph node, then cost would be the length or weight of the edges between nodes. When the routing algorithm determines how to pass network packets from one node to another, it will use this cost to determine an efficient path.

`nodecost` Cost to a particular node on the mesh, and overrides whatever is set in `cost`.

in foo.yml

    tcp-listeners:
      - port: 2222
        cost: 1.0
        nodecost:
          bar: 1.6
          fish: 2.0

This means packets sent to fish have a cost of 2.0, whereas packets sent to bar have a cost of 1.6. If haz joined the mesh, it would get a cost of 1.0 since it’s not in the nodecost map.

The costs on both ends of the connection must match. For example, the `tcp-peers` configuration on `fish` must have a cost of `2.0`, otherwise the connection will be refused.

in fish.yml

    tcp-peers:
      - address: localhost:2222
        cost: 2.0