Jenkins version 1.461.

I try to create Slave Jenkins on Windows 7 machine (master is on Linux) using Java Web start.
1. I connect master Jenkins via browser on Windows machine
2. I go to "Management Nodes"
3. I select the slave node and configuration.
4. When I "launch agent from browser on slave" I get error message

"java.lang.Exception: http://<master jenkins machine>:8080/tcpSlaveAgentListener/ is invalid: -1 null at hudson.remoting.Engine.run(engine.java:179)".

See the attachments.

There is a firewall between slave and master and I have set on master "system configuration" in "Enable security" TCP port for JNLP slave agent: fixed: 20999. This port is open in the firewall.

What could be wrong?
I reboot Master Jenkins but same error message.
I deleted slave node and created a new -> same message
At the very fist time needed files was copied from master to slave into C:\Jenkins folder, but now it doesn't copy nothing.

"Enable security" is unchecked every time, but when I check it I can see setting for the fixed port.

Let me know what more information you need?