If an Init Script is passed there are three sessions opened but only one of them is closed. At the end of the init script processing, the initial sessions timeout and the ssh sessions timeout.

Launching slave agent: java -jar /tmp/slave.jar
<===[JENKINS REMOTING CAPACITY]===>Slave.jar version: 2.33
This is a Unix slave
Evacuated stdout
Slave successfully connected and online
ERROR: Connection terminated
java.io.IOException: Unexpected termination of the channel
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:50)
Caused by: java.io.EOFException
at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2596)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1317)
at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369)
at hudson.remoting.Command.readFrom(Command.java:92)
at hudson.remoting.ClassicCommandTransport.read(ClassicCommandTransport.java:71)
at hudson.remoting.SynchronousCommandTransport$ReaderThread.run(SynchronousCommandTransport.java:48)