NetCallback is a Java application that allows the export of TCP and UDP ports behind a firewall to hosts outside the firewall. NetCallback is a Java application that allows the export of TCP and UDP ports behind a firewall to hosts outside the firewall. This may be useful in some cases, for example, centralized control of the test (demo) networks, or connect to applets running in browsers.NetCallback consists of a public and a private server. The public server running on a host outside the firewall and is responsible for receiving requests for transmission connection port. The private server running on a machine behind the firewall and is responsible for communicating with the public server and the TCP connection protected and / or UDP service for customers of public server. The connection between the public and private could possibly be encrypted using SSL.Note that firewalls exist to protect internal services from external access, and therefore must be very cautious before creating a hole in one ! As indicated in the copyright notice, this program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY, without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.Users are responsible to check their policy use the network for possible violations before using this software. Use at your own risk! NetCallback The service requires the implementation of two network daemons. The first daemon running on a machine behind the firewall and is called PrivateServer. The second daemon is running on a host outside the firewall and is called PublicServer.The PublicServer is invoked with three port numbers. The first port number is used to receive the connection request from the PrivateServer (service port). The second port number is used by clients to connect to the endpoint TCP port forwarding (port forwarding), and the third for UDP.The PrivateServer is invoked with the host name and port number of service of PublicServer. In addition, the PrivateServer must be provided with both the address and TCP port number and / or an internal UDP to be exported.