In this example we are going to demonstrate how to use the custom form of the ALPN extension introduced in JDK 9. ALPN is used to negotiate the application protocol between the client and the server during TLS handshake.
In the source folder there is a CustomALPN project that provides an implementation of a simple TLS client and a TLS server.
Specify using the ALPN extension that the client supports the protocol1 and protocol2 protocols and the server supports the protocol1 protocol only if the negotiated cryptographic cipher is RC4 and the packet buffer size is bigger than 1024 bytes (hint: use the setApplicationProtocols() method on the proper instance in the provided implementation on the client and the setHandshakeApplicationProtocolSelector() method on the proper instance on the server).
Use the compile.sh script to compile the project:
$ ./compile.sh
Run the compiled com.project.Server class with the run_server.sh script:
$ ./run_server.sh
Run the compiled com.project.Client class with the run_client.sh script and observe the negotiated protocol (must be protocol2):
$ ./run_client.sh