cmd, node: initialize ports with --instance

cmd/utils, node: const for listen and disc ports

amend usage description

cmd/geth/main.go

@@ -127,6 +127,7 @@ var (
 		utils.NoDiscoverFlag,
 		utils.DiscoveryV4Flag,
 		utils.DiscoveryV5Flag,
+		utils.InstanceFlag,
 		utils.LegacyDiscoveryV5Flag, // deprecated
 		utils.NetrestrictFlag,
 		utils.NodeKeyFileFlag,

cmd/utils/flags.go

@@ -114,6 +114,13 @@ var (
 		Usage:    "Minimum free disk space in MB, once reached triggers auto shut down (default = --cache.gc converted to MB, 0 = disabled)",
 		Category: flags.EthCategory,
 	}
+	InstanceFlag = &cli.IntFlag{
+		Name:     "instance",
+		Usage:    "Configures the ports to avoid conflicts when running multiple nodes on the same machine. Maximum is 200. Changes to the following port numbers: - port = default + `instance` - 1 - discovery.port = default + `instance` - 1 - authrpc.port = default + `instance`*100 - 100 - http.port = default - `instance` + 1 - ws.port = default + `instance`*2 - 2",
+		Value:    1,
+		Category: flags.EthCategory,
+	}
+
 	KeyStoreDirFlag = &flags.DirectoryFlag{
 		Name:     "keystore",
 		Usage:    "Directory for the keystore (default = inside the datadir)",
@@ -1386,6 +1393,7 @@ func SetP2PConfig(ctx *cli.Context, cfg *p2p.Config) {
 
 // SetNodeConfig applies node-related command line flags to the config.
 func SetNodeConfig(ctx *cli.Context, cfg *node.Config) {
+	setInstance(ctx, cfg)
 	SetP2PConfig(ctx, &cfg.P2P)
 	setIPC(ctx, cfg)
 	setHTTP(ctx, cfg)
@@ -2216,3 +2224,24 @@ func MakeTrieDatabase(ctx *cli.Context, disk ethdb.Database, preimage bool, read
 	}
 	return triedb.NewDatabase(disk, config)
 }
+
+// setInstance configures the port numbers for the given instance.
+func setInstance(ctx *cli.Context, cfg *node.Config) {
+	if ctx.IsSet(InstanceFlag.Name) {
+		cfg.Instance = ctx.Int(InstanceFlag.Name)
+	}
+
+	if cfg.Instance > 200 {
+		Fatalf("Instance number %d is too high, maximum is 200", cfg.Instance)
+	}
+
+	if cfg.Instance == 1 { // using default ports
+		return
+	}
+
+	cfg.AuthPort = node.DefaultConfig.AuthPort + cfg.Instance*100 - 100
+	cfg.HTTPPort = node.DefaultHTTPPort - cfg.Instance + 1
+	cfg.WSPort = node.DefaultWSPort + cfg.Instance*2 - 2
+	cfg.P2P.ListenAddr = fmt.Sprintf(":%d", node.DefaultListenPort+cfg.Instance-1)
+	cfg.P2P.DiscAddr = fmt.Sprintf(":%d", node.DefaultDiscPort+cfg.Instance-1)
+}

node/config.go

@@ -211,6 +211,8 @@ type Config struct {
 	EnablePersonal bool `toml:"-"`
 
 	DBEngine string `toml:",omitempty"`
+
+	Instance int `toml:",omitempty"`
 }
 
 // IPCEndpoint resolves an IPC endpoint based on a configured value, taking into

node/defaults.go

@@ -17,6 +17,7 @@
 package node
 
 import (
+	"fmt"
 	"os"
 	"os/user"
 	"path/filepath"
@@ -28,12 +29,14 @@ import (
 )
 
 const (
-	DefaultHTTPHost = "localhost" // Default host interface for the HTTP RPC server
-	DefaultHTTPPort = 8545        // Default TCP port for the HTTP RPC server
-	DefaultWSHost   = "localhost" // Default host interface for the websocket RPC server
-	DefaultWSPort   = 8546        // Default TCP port for the websocket RPC server
-	DefaultAuthHost = "localhost" // Default host interface for the authenticated apis
-	DefaultAuthPort = 8551        // Default port for the authenticated apis
+	DefaultHTTPHost   = "localhost" // Default host interface for the HTTP RPC server
+	DefaultHTTPPort   = 8545        // Default TCP port for the HTTP RPC server
+	DefaultWSHost     = "localhost" // Default host interface for the websocket RPC server
+	DefaultWSPort     = 8546        // Default TCP port for the websocket RPC server
+	DefaultAuthHost   = "localhost" // Default host interface for the authenticated apis
+	DefaultAuthPort   = 8551        // Default port for the authenticated apis
+	DefaultListenPort = 30303       // Default port for the TCP listening address
+	DefaultDiscPort   = 30303       // Default port for the UDP discovery address
 )
 
 const (
@@ -68,11 +71,12 @@ var DefaultConfig = Config{
 	BatchResponseMaxSize: 25 * 1000 * 1000,
 	GraphQLVirtualHosts:  []string{"localhost"},
 	P2P: p2p.Config{
-		ListenAddr: ":30303",
+		ListenAddr: fmt.Sprintf(":%d", DefaultListenPort),
 		MaxPeers:   50,
 		NAT:        nat.Any(),
 	},
 	DBEngine: "", // Use whatever exists, will default to Pebble if non-existent and supported
+	Instance: 1,
 }
 
 // DefaultDataDir is the default data directory to use for the databases and other