Akka: Simple Akka Cluster not working. - scala

Question

We are creating simple akka cluster sample and follow Akka In Action book. we are creating 3 seed nodes as mention in following code:
akka {
loglevel = INFO
stdout-loglevel = INFO
event-handlers = ["akka.event.Logging$DefaultLogger"]
log-dead-letters = 0
log-dead-letters-during-shutdown = off
actor {
provider = cluster
}
remote {
enabled-transport = ["akka.remote.netty.tcp"]
log-remote-lifecycle-events = off
netty.tcp {
hostname = "127.0.0.1"
hostname = ${?HOST}
port = ${?PORT}
}
}
cluster {
seed-nodes = [
"akka.tcp://words#127.0.0.1:2551",
"akka.tcp://words#127.0.0.1:2552",
"akka.tcp://words#127.0.0.1:2553"
]
roles = ["seed"]
role {
seed.min-nr-of-members = 1
}
}
}
Actor system code:
object Launcher extends App {
val seedConfig = ConfigFactory.load("seed")
val seedSystem = ActorSystem("words", seedConfig)
}
When start actor system from one terminal, the seed node load but according to logs, port 2552 is used but my expectations are 2551. After opening second terminal when trying to run again actor system, I am facing following exception:
[ERROR] [03/10/2017 15:51:45.245] [words-akka.remote.default-remote-dispatcher-13] [NettyTransport(akka://words)] failed to bind to /127.0.0.1:2552, shutting down Netty transport
[error] (run-main-0) org.jboss.netty.channel.ChannelException: Failed to bind to: /127.0.0.1:2552
org.jboss.netty.channel.ChannelException: Failed to bind to: /127.0.0.1:2552
at org.jboss.netty.bootstrap.ServerBootstrap.bind(ServerBootstrap.java:272)
at akka.remote.transport.netty.NettyTransport.$anonfun$listen$1(NettyTransport.scala:417)
at scala.util.Success.$anonfun$map$1(Try.scala:251)
at scala.util.Success.map(Try.scala:209)
This error is generate because, in first terminal our port 2552 is used but not sure why second time same port is use. Our assumptions are, maybe configurations is not loaded. So, how we can fix this ?