network: add ability to specify port for P2P version exchange

pkg/config/application_config.go

@@ -11,6 +11,7 @@ import (
 // ApplicationConfiguration config specific to the node.
 type ApplicationConfiguration struct {
 	Address           string                  `yaml:"Address"`
+	AnnouncedNodePort uint16                  `yaml:"AnnouncedPort"`
 	AttemptConnPeers  int                     `yaml:"AttemptConnPeers"`
 	DBConfiguration   storage.DBConfiguration `yaml:"DBConfiguration"`
 	DialTimeout       time.Duration           `yaml:"DialTimeout"`

pkg/network/server.go

@@ -1278,8 +1278,14 @@ func (s *Server) broadcastTxLoop() {
 	}
 }
 
-// Port returns actual server port. It may differs from that of server.Config.
+// Port returns a server port that should be used in P2P version exchange. In
+// case if `AnnouncedPort` is set in the server.Config, the announced node port
+// will be returned (e.g. consider the node running behind NAT). If `AnnouncedPort`
+// isn't set, the port returned may still differs from that of server.Config.
 func (s *Server) Port() (uint16, error) {
+	if s.AnnouncedPort != 0 {
+		return s.ServerConfig.AnnouncedPort, nil
+	}
 	var port uint16
 	_, portStr, err := net.SplitHostPort(s.transport.Address())
 	if err != nil {

pkg/network/server_config.go

@@ -31,7 +31,10 @@ type (
 		// Address. Example: "127.0.0.1".
 		Address string
 
-		// Port. Example: 20332.
+		// AnnouncedPort is an announced node port for P2P version exchange.
+		AnnouncedPort uint16
+
+		// Port is the actual node port it is bound to. Example: 20332.
 		Port uint16
 
 		// The network mode the server will operate on.
@@ -92,6 +95,7 @@ func NewServerConfig(cfg config.Config) ServerConfig {
 	return ServerConfig{
 		UserAgent:         cfg.GenerateUserAgent(),
 		Address:           appConfig.Address,
+		AnnouncedPort:     appConfig.AnnouncedNodePort,
 		Port:              appConfig.NodePort,
 		Net:               protoConfig.Magic,
 		Relay:             appConfig.Relay,