Receive messages using Waku Filter === WakuFilter is a protocol that enables subscribing to messages that a peer receives. You can find Waku Filter's specifications on [Vac RFC](https://rfc.vac.dev/spec/12/). This is a more lightweight version of WakuRelay specifically designed for bandwidth restricted devices. This is due to the fact that light nodes subscribe to full-nodes and only receive the messages they desire. ## Create a waku instance ```go package main import ( "context" "fmt" "github.com/waku-org/go-waku/waku/v2/node" "github.com/waku-org/go-waku/waku/v2/protocol/filter" ) ... wakuNode, err := node.New(node.WithWakuFilter(false)) if err != nil { fmt.Println(err) return } if err := wakuNode.Start(context.Background()); err != nil { fmt.Println(err) return } ... ``` ### Options One of these options must be specified when instantiating a node supporting the waku relay protocol - `WitWakuFilter(isFullNode, opts ...pubsub.Option)` - enables the waku filter protocol and receives an optional list of options to configure the protocol ## Adding a peer and receiving messages ```go ... peerAddr, err := multiaddr.NewMultiaddr("/dns4/node-01.do-ams3.wakuv2.test.statusim.net/tcp/30303/p2p/16Uiu2HAmPLe7Mzm8TsYUubgCAW1aJoeFScxrLj8ppHFivPo97bUZ") if err != nil { panic(err) } _, err = wakuNode.AddPeer(peerAddr, string(filter.FilterID_v20beta1)) if err != nil { panic(err) } // Setting the content filter cf := filter.ContentFilter{ Topic: "/waku/2/default-waku/proto", ContentTopics: []string{contentTopic}, } _, subscription, err := wakuNode.Filter().Subscribe(context.Background(), cf) if err != nil { panic(err) } for env := range subscription.Chan { fmt.Println("Received msg:", string(value.Message().Payload)) } ... ``` To receive messages sent via the relay protocol, you need to subscribe to a pubsub topic. This can be done via any of these functions: - `wakuNode.Filter().Subscribe(ctx, contentFilter, opts)` - subscribes to receive messages that match a specific contentFilter This function return a `Filter` subscrition. To stop receiving messages in this channel `wakuNode.UnsubscribeByFilter(ctx, theFilter)` can be executed which will close the subscription and channel for the filter. `wakuNode.Unsubscribe` and `wakuNode.UnsubscribeFilterByID` are also available for similar purposes If no options are specified when subscribing to a filter node, go-waku will automatically choose the peer to subscribe to. This behaviour can be controlled via options: ### Options - `filter.WithPeer(peerID)` - use an specific peer ID (which should be part of the node peerstore) to receive the messages from - `filter.WithAutomaticPeerSelection(host)` - automatically select a peer that supports filter protocol from the peerstore to receive the messages from - `filter.WithFastestPeerSelection(ctx)` - automatically select a peer based on its ping reply time