Merge pull request #20 from muun/release-v2.2.4

Release 2.2.4
2023-06-20 12:02:38 -03:00 · 2023-06-20 12:02:38 -03:00 · 124e9fa1bc
parent ed2c88afac 72f9f69035
commit 124e9fa1bc
8 changed files with 177 additions and 97 deletions
--- a/electrum/client.go
+++ b/electrum/client.go
@ -36,6 +36,7 @@ type Client struct {
 	nextRequestID int
 	conn          net.Conn
 	log           *utils.Logger
+	requireTls    bool
 }

 // Request models the structure of all Electrum protocol requests.
@ -110,9 +111,10 @@ type ServerFeatures struct {
 type Param = interface{}

 // NewClient creates an initialized Client instance.
-func NewClient() *Client {
+func NewClient(requireTls bool) *Client {
 	return &Client{
-		log: utils.NewLogger(defaultLoggerTag),
+		log:        utils.NewLogger(defaultLoggerTag),
+		requireTls: requireTls,
 	}
 }

@ -334,6 +336,9 @@ func (c *Client) ListUnspentBatch(indexHashes []string) ([][]UnspentRef, error)
 }

 func (c *Client) establishConnection() error {
+	// We first try to connect over TCP+TLS
+	// If we fail and requireTls is false, we try over TCP
+
 	// TODO: check if insecure is necessary
 	config := &tls.Config{
 		InsecureSkipVerify: true,
@ -343,12 +348,22 @@ func (c *Client) establishConnection() error {
 		Timeout: connectionTimeout,
 	}

-	conn, err := tls.DialWithDialer(dialer, "tcp", c.Server, config)
+	tlsConn, err := tls.DialWithDialer(dialer, "tcp", c.Server, config)
+	if err == nil {
+		c.conn = tlsConn
+		return nil
+	}
+	if c.requireTls {
+		return err
+	}
+
+	conn, err := net.DialTimeout("tcp", c.Server, connectionTimeout)
 	if err != nil {
 		return err
 	}

 	c.conn = conn
+
 	return nil
 }

--- a/electrum/pool.go
+++ b/electrum/pool.go
@ -7,11 +7,11 @@ type Pool struct {
 }

 // NewPool creates an initialized Pool with a `size` number of clients.
-func NewPool(size int) *Pool {
+func NewPool(size int, requireTls bool) *Pool {
 	nextClient := make(chan *Client, size)

 	for i := 0; i < size; i++ {
-		nextClient <- NewClient()
+		nextClient <- NewClient(requireTls)
 	}

 	return &Pool{nextClient}
--- a/electrum/servers.go
+++ b/electrum/servers.go
@ -5,17 +5,21 @@ import "sync/atomic"
 // ServerProvider manages a rotating server list, from which callers can pull server addresses.
 type ServerProvider struct {
 	nextIndex int32
+	servers   []string
 }

 // NewServerProvider returns an initialized ServerProvider.
-func NewServerProvider() *ServerProvider {
-	return &ServerProvider{-1}
+func NewServerProvider(servers []string) *ServerProvider {
+	return &ServerProvider{
+		nextIndex: -1,
+		servers:   servers,
+	}
 }

 // NextServer returns an address from the rotating list. It's thread-safe.
 func (p *ServerProvider) NextServer() string {
 	index := int(atomic.AddInt32(&p.nextIndex, 1))
-	return PublicServers[index%len(PublicServers)]
+	return p.servers[index%len(p.servers)]
 }

 // PublicServers list.
@ -29,72 +33,73 @@ func (p *ServerProvider) NextServer() string {
 // See `cmd/survey/main.go`
 var PublicServers = []string{
 	// Fast servers with batching
-	"blackie.c3-soft.com:57002",             // impl: Fulcrum 1.6.0, batching: true, ttc: 0.72, speed: 97, from: fortress.qtornado.com:443
-	"fullnode.titanconnect.ca:50002",        // impl: Fulcrum 1.6.0, batching: true, ttc: 0.66, speed: 86, from: fortress.qtornado.com:443
-	"de.poiuty.com:50002",                   // impl: Fulcrum 1.6.0, batching: true, ttc: 0.76, speed: 78, from: fortress.qtornado.com:443
-	"2ex.digitaleveryware.com:50002",        // impl: ElectrumX 1.16.0, batching: true, ttc: 0.68, speed: 68, from: fortress.qtornado.com:443
-	"fortress.qtornado.com:443",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.77, speed: 67, from:
-	"hodlers.beer:50002",                    // impl: ElectrumX 1.16.0, batching: true, ttc: 0.74, speed: 64, from: fortress.qtornado.com:443
-	"f.keff.org:50002",                      // impl: Fulcrum 1.6.0, batching: true, ttc: 0.76, speed: 60, from: fortress.qtornado.com:443
-	"e2.keff.org:50002",                     // impl: Fulcrum 1.6.0, batching: true, ttc: 0.75, speed: 58, from:
-	"electrum.stippy.com:50002",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.75, speed: 56, from: fortress.qtornado.com:443
-	"electrum.privateservers.network:50002", // impl: ElectrumX 1.15.0, batching: true, ttc: 0.83, speed: 52, from: fortress.qtornado.com:443
-	"fulcrum.grey.pw:51002",                 // impl: Fulcrum 1.6.0, batching: true, ttc: 0.79, speed: 49, from: fortress.qtornado.com:443
-	"btc.electroncash.dk:60002",             // impl: Fulcrum 1.6.0, batching: true, ttc: 0.79, speed: 49, from: fortress.qtornado.com:443
-	"node.degga.net:50002",                  // impl: ElectrumX 1.16.0, batching: true, ttc: 0.59, speed: 46, from: fortress.qtornado.com:443
-	"e.keff.org:50002",                      // impl: ElectrumX 1.10.0, batching: true, ttc: 0.76, speed: 45, from:
-	"bitcoin.aranguren.org:50002",           // impl: Fulcrum 1.6.0, batching: true, ttc: 1.25, speed: 41, from:
-	"electrum.helali.me:50002",              // impl: Fulcrum 1.6.0, batching: true, ttc: 1.20, speed: 38, from: fortress.qtornado.com:443
-	"node1.btccuracao.com:50002",            // impl: ElectrumX 1.16.0, batching: true, ttc: 0.79, speed: 33, from: fortress.qtornado.com:443
-	"ASSUREDLY.not.fyi:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.66, speed: 20, from: electrumx.erbium.eu:50002
-	"assuredly.not.fyi:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.74, speed: 20, from: fortress.qtornado.com:443
+	"electrum.coinext.com.br:50002",         // impl: ElectrumX 1.14.0, batching: true, ttc: 0.15, speed: 113, from:
+	"fulcrum.sethforprivacy.com:50002",      // impl: Fulcrum 1.9.0, batching: true, ttc: 0.55, speed: 96, from:
+	"mainnet.foundationdevices.com:50002",   // impl: Fulcrum 1.8.2, batching: true, ttc: 0.54, speed: 88, from:
+	"btc.lastingcoin.net:50002",             // impl: Fulcrum 1.7.0, batching: true, ttc: 0.74, speed: 73, from:
+	"vmd71287.contaboserver.net:50002",      // impl: Fulcrum 1.9.0, batching: true, ttc: 0.60, speed: 70, from:
+	"de.poiuty.com:50002",                   // impl: Fulcrum 1.8.2, batching: true, ttc: 0.87, speed: 70, from:
+	"electrum.jochen-hoenicke.de:50006",     // impl: Fulcrum 1.8.2, batching: true, ttc: 0.83, speed: 69, from:
+	"btc.cr.ypto.tech:50002",                // impl: Fulcrum 1.9.0, batching: true, ttc: 0.81, speed: 65, from:
+	"e.keff.org:50002",                      // impl: Fulcrum 1.8.2, batching: true, ttc: 0.82, speed: 65, from:
+	"vmd104014.contaboserver.net:50002",     // impl: Fulcrum 1.9.0, batching: true, ttc: 0.58, speed: 64, from:
+	"e2.keff.org:50002",                     // impl: Fulcrum 1.8.2, batching: true, ttc: 0.83, speed: 64, from:
+	"fulcrum.grey.pw:51002",                 // impl: Fulcrum 1.9.0, batching: true, ttc: 0.81, speed: 63, from:
+	"fortress.qtornado.com:443",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.84, speed: 62, from:
+	"f.keff.org:50002",                      // impl: Fulcrum 1.8.2, batching: true, ttc: 0.89, speed: 62, from:
+	"2ex.digitaleveryware.com:50002",        // impl: ElectrumX 1.16.0, batching: true, ttc: 0.71, speed: 61, from:
+	"electrum.petrkr.net:50002",             // impl: Fulcrum 1.9.0, batching: true, ttc: 0.84, speed: 58, from:
+	"electrum.stippy.com:50002",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.80, speed: 57, from:
+	"electrum0.snel.it:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.80, speed: 56, from:
+	"ru.poiuty.com:50002",                   // impl: Fulcrum 1.8.2, batching: true, ttc: 0.99, speed: 56, from:
+	"electrum.privateservers.network:50002", // impl: ElectrumX 1.15.0, batching: true, ttc: 0.85, speed: 49, from:
+	"btc.electroncash.dk:60002",             // impl: Fulcrum 1.9.0, batching: true, ttc: 0.92, speed: 48, from:
+	"bitcoin.aranguren.org:50002",           // impl: Fulcrum 1.8.2, batching: true, ttc: 1.19, speed: 48, from:
+	"electrum.bitcoinserver.nl:50514",       // impl: Fulcrum 1.8.1, batching: true, ttc: 0.85, speed: 44, from:
+	"btc.prompt.cash:61002",                 // impl: Fulcrum 1.8.1, batching: true, ttc: 1.22, speed: 44, from:
+	"fulc.bot.nu:50002",                     // impl: Fulcrum 1.7.0, batching: true, ttc: 1.04, speed: 35, from:
+	"bolt.schulzemic.net:50002",             // impl: Fulcrum 1.8.2, batching: true, ttc: 0.96, speed: 33, from:
+	"node1.btccuracao.com:50002",            // impl: ElectrumX 1.16.0, batching: true, ttc: 0.90, speed: 25, from:

 	// Other servers
-	"smmalis37.ddns.net:50002",            // impl: ElectrumX 1.16.0, batching: true, ttc: 0.56, speed: 19, from: fortress.qtornado.com:443
-	"electrumx.papabyte.com:50002",        // impl: ElectrumX 1.16.0, batching: true, ttc: 0.95, speed: 19, from: fortress.qtornado.com:443
-	"electrum.bitaroo.net:50002",          // impl: ElectrumX 1.16.0, batching: true, ttc: 0.98, speed: 19, from: fortress.qtornado.com:443
-	"electrum.exan.tech:443",              // impl: ElectrumX 1.16.0, batching: true, ttc: 1.08, speed: 19, from: fortress.qtornado.com:443
-	"electrum-fulcrum.toggen.net:50002",   // impl: Fulcrum 1.6.0, batching: true, ttc: 1.47, speed: 16, from: fortress.qtornado.com:443
-	"vmd84592.contaboserver.net:50002",    // impl: ElectrumX 1.16.0, batching: true, ttc: 0.79, speed: 14, from: fortress.qtornado.com:443
-	"gd42.org:50002",                      // impl: ElectrumX 1.16.0, batching: true, ttc: 0.50, speed: 12, from: fortress.qtornado.com:443
-	"vmd63185.contaboserver.net:50002",    // impl: ElectrumX 1.16.0, batching: true, ttc: 0.75, speed: 12, from: fortress.qtornado.com:443
-	"alfa.cryptotrek.online:50002",        // impl: ElectrumX 1.16.0, batching: true, ttc: 0.75, speed: 12, from: fortress.qtornado.com:443
-	"electrumx.ultracloud.tk:50002",       // impl: ElectrumX 1.16.0, batching: true, ttc: 0.76, speed: 12, from: fortress.qtornado.com:443
-	"electrum.brainshome.de:50002",        // impl: ElectrumX 1.16.0, batching: true, ttc: 0.89, speed: 12, from: fortress.qtornado.com:443
-	"ragtor.duckdns.org:50002",            // impl: ElectrumX 1.16.0, batching: true, ttc: 0.91, speed: 12, from: bitcoin.aranguren.org:50002
-	"94.23.247.135:50002",                 // impl: ElectrumX 1.16.0, batching: true, ttc: 6.80, speed: 12, from: fortress.qtornado.com:443
-	"eai.coincited.net:50002",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.12, speed: 11, from: electrumx.erbium.eu:50002
-	"142.93.6.38:50002",                   // impl: ElectrumX 1.16.0, batching: true, ttc: 0.56, speed: 11, from: fortress.qtornado.com:443
-	"157.245.172.236:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.62, speed: 11, from: fortress.qtornado.com:443
-	"electrum.kendigisland.xyz:50002",     // impl: ElectrumX 1.16.0, batching: true, ttc: 0.68, speed: 11, from: fortress.qtornado.com:443
-	"btc.lastingcoin.net:50002",           // impl: ElectrumX 1.16.0, batching: true, ttc: 0.74, speed: 11, from: fortress.qtornado.com:443
-	"xtrum.com:50002",                     // impl: ElectrumX 1.16.0, batching: true, ttc: 0.75, speed: 11, from: electrumx.erbium.eu:50002
-	"blkhub.net:50002",                    // impl: ElectrumX 1.16.0, batching: true, ttc: 0.76, speed: 11, from: fortress.qtornado.com:443
-	"electrumx.erbium.eu:50002",           // impl: ElectrumX 1.16.0, batching: true, ttc: 0.78, speed: 11, from:
-	"185.64.116.15:50002",                 // impl: ElectrumX 1.16.0, batching: true, ttc: 0.79, speed: 11, from: bitcoin.aranguren.org:50002
-	"188.165.206.215:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.81, speed: 11, from: fortress.qtornado.com:443
-	"ex03.axalgo.com:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.92, speed: 11, from: fortress.qtornado.com:443
-	"electrum.bitcoinlizard.net:50002",    // impl: ElectrumX 1.16.0, batching: true, ttc: 0.98, speed: 11, from: fortress.qtornado.com:443
-	"btce.iiiiiii.biz:50002",              // impl: ElectrumX 1.16.0, batching: true, ttc: 1.02, speed: 11, from: fortress.qtornado.com:443
-	"btc.ocf.sh:50002",                    // impl: ElectrumX 1.16.0, batching: true, ttc: 1.15, speed: 11, from: fortress.qtornado.com:443
-	"68.183.188.105:50002",                // impl: ElectrumX 1.16.0, batching: true, ttc: 1.36, speed: 11, from: fortress.qtornado.com:443
-	"vmd71287.contaboserver.net:50002",    // impl: ElectrumX 1.16.0, batching: true, ttc: 0.60, speed: 10, from: fortress.qtornado.com:443
-	"2electrumx.hopto.me:56022",           // impl: ElectrumX 1.16.0, batching: true, ttc: 0.89, speed: 10, from: fortress.qtornado.com:443
-	"electrum.emzy.de:50002",              // impl: ElectrumX 1.16.0, batching: true, ttc: 1.15, speed: 10, from:
-	"electrumx.electricnewyear.net:50002", // impl: ElectrumX 1.15.0, batching: true, ttc: 0.66, speed: 9, from:
-	"walle.dedyn.io:50002",                // impl: ElectrumX 1.16.0, batching: true, ttc: 0.76, speed: 8, from: fortress.qtornado.com:443
-	"caleb.vegas:50002",                   // impl: ElectrumX 1.16.0, batching: true, ttc: 0.80, speed: 8, from: fortress.qtornado.com:443
-	"electrum.neocrypto.io:50002",         // impl: ElectrumX 1.16.0, batching: true, ttc: 0.69, speed: 7, from: fortress.qtornado.com:443
-	"guichet.centure.cc:50002",            // impl: ElectrumX 1.16.0, batching: true, ttc: 0.71, speed: 7, from: fortress.qtornado.com:443
-	"167.172.42.31:50002",                 // impl: ElectrumX 1.16.0, batching: true, ttc: 0.75, speed: 7, from: fortress.qtornado.com:443
-	"2AZZARITA.hopto.org:50002",           // impl: ElectrumX 1.16.0, batching: true, ttc: 0.77, speed: 7, from: fortress.qtornado.com:443
-	"jonas.reptiles.se:50002",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.95, speed: 7, from: fortress.qtornado.com:443
-	"167.172.226.175:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.61, speed: 6, from: fortress.qtornado.com:443
-	"electrum-btc.leblancnet.us:50002",    // impl: ElectrumX 1.15.0, batching: true, ttc: 0.64, speed: 6, from: fortress.qtornado.com:443
-	"104.248.139.211:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.90, speed: 6, from: fortress.qtornado.com:443
-	"elx.bitske.com:50002",                // impl: ElectrumX 1.16.0, batching: true, ttc: 1.01, speed: 6, from: fortress.qtornado.com:443
-	"kareoke.qoppa.org:50002",             // impl: ElectrumX 1.16.0, batching: true, ttc: 1.18, speed: 6, from: electrumx.erbium.eu:50002
-	"ex.btcmp.com:50002",                  // impl: ElectrumX 1.16.0, batching: true, ttc: 1.12, speed: 5, from: fortress.qtornado.com:443
-	"bitcoins.sk:56002",                   // impl: ElectrumX 1.14.0, batching: true, ttc: 0.77, speed: 3, from: fortress.qtornado.com:443
-	"73.92.198.54:50002",                  // impl: ElectrumX 1.15.0, batching: true, ttc: 5.57, speed: 0, from: fortress.qtornado.com:443
+	"xtrum.com:50002",                       // impl: ElectrumX 1.16.0, batching: true, ttc: 0.91, speed: 19, from: fulcrum.sethforprivacy.com:50002
+	"electrum.bitaroo.net:50002",            // impl: ElectrumX 1.16.0, batching: true, ttc: 1.04, speed: 19, from:
+	"btce.iiiiiii.biz:50002",                // impl: ElectrumX 1.16.0, batching: true, ttc: 1.07, speed: 19, from: electrum.coinext.com.br:50002
+	"electrum.emzy.de:50002",                // impl: ElectrumX 1.16.0, batching: true, ttc: 1.17, speed: 19, from:
+	"alviss.coinjoined.com:50002",           // impl: ElectrumX 1.15.0, batching: true, ttc: 1.15, speed: 17, from:
+	"2AZZARITA.hopto.org:50002",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.81, speed: 16, from: electrum.coinext.com.br:50002
+	"vmd104012.contaboserver.net:50002",     // impl: Fulcrum 1.9.0, batching: true, ttc: 1.25, speed: 16, from:
+	"electrum.bitcoinlizard.net:50002",      // impl: ElectrumX 1.16.0, batching: true, ttc: 4.99, speed: 14, from:
+	"btc.ocf.sh:50002",                      // impl: ElectrumX 1.16.0, batching: true, ttc: 1.19, speed: 12, from:
+	"bitcoins.sk:56002",                     // impl: ElectrumX 1.14.0, batching: true, ttc: 0.80, speed: 11, from:
+	"electrum-btc.leblancnet.us:50002",      // impl: ElectrumX 1.16.0, batching: true, ttc: 1.04, speed: 11, from:
+	"helicarrier.bauerj.eu:50002",           // impl: ElectrumX 1.10.0, batching: true, ttc: 0.96, speed: 10, from:
+	"electrum.neocrypto.io:50002",           // impl: ElectrumX 1.16.0, batching: true, ttc: 0.69, speed: 7, from:
+	"caleb.vegas:50002",                     // impl: ElectrumX 1.16.0, batching: true, ttc: 0.71, speed: 7, from:
+	"smmalis37.ddns.net:50002",              // impl: ElectrumX 1.16.0, batching: true, ttc: 0.77, speed: 7, from:
+	"2azzarita.hopto.org:50002",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.78, speed: 7, from: fulcrum.sethforprivacy.com:50002
+	"electrum.kendigisland.xyz:50002",       // impl: ElectrumX 1.16.0, batching: true, ttc: 0.79, speed: 7, from:
+	"electrum.hsmiths.com:50002",            // impl: ElectrumX 1.10.0, batching: true, ttc: 0.90, speed: 7, from:
+	"vmd63185.contaboserver.net:50002",      // impl: ElectrumX 1.16.0, batching: true, ttc: 0.92, speed: 7, from:
+	"blkhub.net:50002",                      // impl: ElectrumX 1.16.0, batching: true, ttc: 0.94, speed: 7, from:
+	"electrum.mmitech.info:50002",           // impl: ElectrumX 1.16.0, batching: true, ttc: 0.95, speed: 7, from:
+	"elx.bitske.com:50002",                  // impl: ElectrumX 1.16.0, batching: true, ttc: 1.17, speed: 7, from:
+	"bitcoin.lu.ke:50002",                   // impl: ElectrumX 1.16.0, batching: true, ttc: 1.21, speed: 7, from:
+	"ex05.axalgo.com:50002",                 // impl: ElectrumX 1.16.0, batching: true, ttc: 1.21, speed: 7, from:
+	"walle.dedyn.io:50002",                  // impl: ElectrumX 1.16.0, batching: true, ttc: 1.23, speed: 7, from:
+	"eai.coincited.net:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.34, speed: 6, from:
+	"2electrumx.hopto.me:56022",             // impl: ElectrumX 1.16.0, batching: true, ttc: 0.93, speed: 6, from:
+	"hodlers.beer:50002",                    // impl: ElectrumX 1.16.0, batching: true, ttc: 1.03, speed: 6, from:
+	"kareoke.qoppa.org:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 1.13, speed: 6, from:
+	"ASSUREDLY.not.fyi:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.85, speed: 4, from:
+	"electrumx.alexridevski.net:50002",      // impl: ElectrumX 1.16.0, batching: true, ttc: 0.87, speed: 4, from:
+	"assuredly.not.fyi:50002",               // impl: ElectrumX 1.16.0, batching: true, ttc: 0.90, speed: 4, from:
+	"ragtor.duckdns.org:50002",              // impl: ElectrumX 1.16.0, batching: true, ttc: 1.07, speed: 4, from:
+	"surely.not.fyi:50002",                  // impl: ElectrumX 1.16.0, batching: true, ttc: 1.20, speed: 4, from:
+	"btc.electrum.bitbitnet.net:50002",      // impl: ElectrumX 1.15.0, batching: true, ttc: 0.71, speed: 3, from:
+	"gods-of-rock.screaminglemur.net:50002", // impl: ElectrumX 1.15.0, batching: true, ttc: 0.92, speed: 3, from:
+	"SURELY.not.fyi:50002",                  // impl: ElectrumX 1.16.0, batching: true, ttc: 1.35, speed: 3, from:
+	"horsey.cryptocowboys.net:50002",        // impl: ElectrumX 1.15.0, batching: true, ttc: 0.61, speed: 2, from:
+	"electrumx-btc.cryptonermal.net:50002",  // impl: ElectrumX 1.15.0, batching: true, ttc: 0.83, speed: 1, from:
+	"electrum.coineuskal.com:50002",         // impl: ElectrumX 1.15.0, batching: true, ttc: 1.73, speed: 0, from: electrum.coinext.com.br:50002
 }
--- a/main.go
+++ b/main.go
@ -14,19 +14,31 @@ import (
 	"github.com/muun/libwallet"
 	"github.com/muun/libwallet/btcsuitew/btcutilw"
 	"github.com/muun/libwallet/emergencykit"
+	"github.com/muun/recovery/electrum"
 	"github.com/muun/recovery/scanner"
 	"github.com/muun/recovery/utils"
 )

+const electrumPoolSize = 6
+
 var debugOutputStream = bytes.NewBuffer(nil)

+type config struct {
+	generateContacts     bool
+	providedElectrum     string
+	usesProvidedElectrum bool
+	onlyScan             bool
+}
+
 func main() {
 	utils.SetOutputStream(debugOutputStream)

-	var generateContacts bool
+	var config config

 	// Pick up command-line arguments:
-	flag.BoolVar(&generateContacts, "generate-contacts", false, "Generate contact addresses")
+	flag.BoolVar(&config.generateContacts, "generate-contacts", false, "Generate contact addresses")
+	flag.StringVar(&config.providedElectrum, "electrum-server", "", "Connect to this electrum server to find funds")
+	flag.BoolVar(&config.onlyScan, "only-scan", false, "Only scan for UTXOs without generating a transaction")
 	flag.Usage = printUsage
 	flag.Parse()
 	args := flag.Args()
@ -40,6 +52,11 @@ func main() {
 	// Welcome!
 	printWelcomeMessage()

+	config.usesProvidedElectrum = len(strings.TrimSpace(config.providedElectrum)) > 0
+	if config.usesProvidedElectrum {
+		validateProvidedElectrum(config.providedElectrum)
+	}
+
 	// We're going to need a few things to move forward with the recovery process. Let's make a list
 	// so we keep them in mind:
 	var recoveryCode string
@ -62,25 +79,41 @@ func main() {

 	decryptedKeys[0].Key.Path = "m/1'/1'" // a little adjustment for legacy users.

-	// Finally, we need the destination address to sweep the funds:
-	destinationAddress = readAddress()
+	if !config.onlyScan {
+		// Finally, we need the destination address to sweep the funds:
+		destinationAddress = readAddress()
+	}

 	sayBlock(`
 		Starting scan of all possible addresses. This will take a few minutes.
 	`)

-	doRecovery(decryptedKeys, destinationAddress, generateContacts)
+	doRecovery(decryptedKeys, destinationAddress, config)

 	sayBlock("We appreciate all kinds of feedback. If you have any, send it to {blue contact@muun.com}\n")
 }

 // doRecovery runs the scan & sweep process, and returns the ID of the broadcasted transaction.
 func doRecovery(
-	decryptedKeys []*libwallet.DecryptedPrivateKey, destinationAddress btcutil.Address, generateContacts bool,
+	decryptedKeys []*libwallet.DecryptedPrivateKey,
+	destinationAddress btcutil.Address,
+	config config,
 ) {

-	addrGen := NewAddressGenerator(decryptedKeys[0].Key, decryptedKeys[1].Key, generateContacts)
-	utxoScanner := scanner.NewScanner()
+	addrGen := NewAddressGenerator(decryptedKeys[0].Key, decryptedKeys[1].Key, config.generateContacts)
+
+	var electrumProvider *electrum.ServerProvider
+	if config.usesProvidedElectrum {
+		electrumProvider = electrum.NewServerProvider([]string{
+			config.providedElectrum,
+		})
+	} else {
+		electrumProvider = electrum.NewServerProvider(electrum.PublicServers)
+	}
+
+	connectionPool := electrum.NewPool(electrumPoolSize, !config.usesProvidedElectrum)
+
+	utxoScanner := scanner.NewScanner(connectionPool, electrumProvider)

 	addresses := addrGen.Stream()

@ -122,6 +155,9 @@ func doRecovery(
 	}

 	say("\n— {white %d} sats total\n", total)
+	if config.onlyScan {
+		return
+	}

 	txOutputAmount, txWeightInBytes, err := sweeper.GetSweepTxAmountAndWeightInBytes(utxos)
 	if err != nil {
@ -145,11 +181,36 @@ func doRecovery(

 	sayBlock(`
 		Transaction sent! You can check the status here: https://mempool.space/tx/%v
-		(it will appear in Blockstream after a short delay)
+		(it will appear in mempool.space after a short delay)

 	`, sweepTx.TxHash().String())
 }

+func validateProvidedElectrum(providedElectrum string) {
+	client := electrum.NewClient(false)
+	err := client.Connect(providedElectrum)
+	defer func(client *electrum.Client) {
+		_ = client.Disconnect()
+	}(client)
+
+	if err != nil {
+		sayBlock(`
+				{red Error!}
+				The Recovery Tool couldn't connect to the provided Electrum server %v.
+
+				If the problem persists, contact {blue support@muun.com}.
+				
+				――― {white error report} ―――
+				%v
+				――――――――――――――――――――
+
+				We're always there to help.
+			`, providedElectrum, err)
+
+		os.Exit(2)
+	}
+}
+
 func exitWithError(err error) {
 	sayBlock(`
 		{red Error!}
@ -351,7 +412,7 @@ func readAddress() btcutil.Address {
 func readFee(totalBalance, weight int64) int64 {
 	sayBlock(`
 		{yellow Enter the fee rate (sats/byte)}
-		Your transaction weighs %v bytes. You can get suggestions in https://bitcoinfees.earn.com/#fees
+		Your transaction weighs %v bytes. You can get suggestions in https://mempool.space/ under "Transaction fees".
 	`, weight)

 	var userInput string
--- a/scanner/scanner.go
+++ b/scanner/scanner.go
@ -9,7 +9,6 @@ import (
 	"github.com/muun/recovery/utils"
 )

-const electrumPoolSize = 6
 const taskTimeout = 15 * time.Minute
 const batchSize = 100

@ -70,10 +69,10 @@ type scanContext struct {
 }

 // NewScanner creates an initialized Scanner.
-func NewScanner() *Scanner {
+func NewScanner(connectionPool *electrum.Pool, electrumProvider *electrum.ServerProvider) *Scanner {
 	return &Scanner{
-		pool:    electrum.NewPool(electrumPoolSize),
-		servers: electrum.NewServerProvider(),
+		pool:    connectionPool,
+		servers: electrumProvider,
 		log:     utils.NewLogger("Scanner"),
 	}
 }
--- a/survey/survey.go
+++ b/survey/survey.go
@ -47,7 +47,7 @@ type surveyTask struct {
 }

 // Values to check whether we're in the same chain (in a previous version, SV servers snuck in)
-var mainnetSomeTx = "1712426823cc94935287a6834f7982723fbb5c808cbe00ec2cf3f582582be4c5"
+var mainnetSomeTx = "985eb411473fa1bbd73efa5e3685edc00366c86b8d4d3f5b969ad59c23f4d959"
 var mainnetGenesisHash = "000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"

 func NewSurvey(config *Config) *Survey {
@ -194,7 +194,7 @@ func (s *Survey) processTask(task *surveyTask) *Result {

 // testConnection returns the server implementation, protocol version and time to connect
 func testConnection(task *surveyTask) (string, string, time.Duration, error) {
-	client := electrum.NewClient()
+	client := electrum.NewClient(true)

 	start := time.Now()
 	err := client.Connect(task.server)
@ -207,7 +207,7 @@ func testConnection(task *surveyTask) (string, string, time.Duration, error) {

 // testsBlockchain returns whether this server is operating on Bitcoin mainnet
 func testBitcoinMainnet(task *surveyTask) (bool, error) {
-	client := electrum.NewClient()
+	client := electrum.NewClient(true)

 	err := client.Connect(task.server)
 	if err != nil {
@ -229,7 +229,7 @@ func testBitcoinMainnet(task *surveyTask) (bool, error) {

 // testBatchSupport returns whether the server successfully responded to a batched request
 func testBatchSupport(task *surveyTask) (bool, error) {
-	client := electrum.NewClient()
+	client := electrum.NewClient(true)

 	err := client.Connect(task.server)
 	if err != nil {
@ -247,7 +247,7 @@ func testBatchSupport(task *surveyTask) (bool, error) {
 // measureSpeed returns the amount of successful ListUnspentBatch calls in SPEED_TEST_DURATION
 // seconds. It assumes batch support was verified beforehand.
 func (s *Survey) measureSpeed(task *surveyTask) (int, error) {
-	client := electrum.NewClient()
+	client := electrum.NewClient(true)

 	err := client.Connect(task.server)
 	if err != nil {
@ -273,7 +273,7 @@ func (s *Survey) measureSpeed(task *surveyTask) (int, error) {

 // getPeers returns the list of peers from a server, or empty if it doesn't responds to the request
 func getPeers(task *surveyTask) ([]string, error) {
-	client := electrum.NewClient()
+	client := electrum.NewClient(true)

 	err := client.Connect(task.server)
 	if err != nil {
--- a/sweeper.go
+++ b/sweeper.go
@ -54,8 +54,8 @@ func (s *Sweeper) BuildSweepTx(utxos []*scanner.Utxo, fee int64) (*wire.MsgTx, e

 func (s *Sweeper) BroadcastTx(tx *wire.MsgTx) error {
 	// Connect to an Electurm server using a fresh client and provider pair:
-	sp := electrum.NewServerProvider() // TODO create servers module, for provider and pool
-	client := electrum.NewClient()
+	sp := electrum.NewServerProvider(electrum.PublicServers) // TODO create servers module, for provider and pool
+	client := electrum.NewClient(true)

 	for !client.IsConnected() {
 		client.Connect(sp.NextServer())
--- a/version.go
+++ b/version.go
@ -3,4 +3,4 @@ package main
 // The OSS tool depends on this file with this content. If you need to change
 // it, change the tool too.

-const version = "2.2.3"
+const version = "2.2.4"