Websocket Java Server/Client implementation

http://akinaru.github.io/websocket-java/

Websocket Server/Client implementation

This project uses HTTP endec project : http://akinaru.github.io/http-endec-java/

Last update 16/05/2015

You will find :

How to launch Websocket Server ?

WebsocketServer server = new WebsocketServer(WEBSOCKET_PORT);
server.start();

you specify the port in WEBSOCKET_PORT

How to monitor my clients connected to server ?

Just add a Listener to server object. You have 3 callbacks that will notify you on client connection change and arrival of client messages

server.addServerEventListener(new IClientEventListener() {

            @Override
            public void onMessageReceivedFromClient(IWebsocketClient client,
                    String message) {
                //all your message received from websocket client will be here
                System.out.println("message received : " + message);
            }

            @Override
            public void onClientConnection(IWebsocketClient client) {
                // when a websocket client connect. This will be called (you can store client object)
                System.out.println("Websocket client has connected");

                client.sendMessage("Hello,I'm a websocket server");

                //client.close(); // this would close the client connection
            }

            @Override
            public void onClientClose(IWebsocketClient client) {
                // when a websocket client connection close. This will be called (you can dismiss client object)
                System.out.println("Websocket client has disconnected");
            }
        });

How to launch a SSL secured websocket server ?

WWebsocketServer server = new WebsocketServer(WEBSOCKET_PORT);

server.setSsl(true); // set SSL to true (default is false)

Then you set your kestore, trustore, type of these certificates, filepath and passwords : 

server.setSSLParams(String KEYSTORE_DEFAULT_TYPE,
            String KEYSTORE_FILE_PATH,
            String TRUSTORE_FILE_PATH,
            String SSL_PROTOCOL,
            String KEYSTORE_PASSWORD,
            String TRUSTORE_PASSWORD);

Here is the description of all of these parameters :

Eventually add event listener as described above and start websocket server : 

server.start();

How to connect a websocket client to server ?

new instance of websocket client to connect to server on HOSTNAME:PORT : 

WebsocketClient clientSocket = new WebsocketClient(HOSTNAME, PORT);

clientSocket.connect();

You can monitor all your event in your websocket client adding a websocket client event listener like this :

clientSocket.addClientSocketEventListener(new IWebsocketClientEventListener() {

                    @Override
                    public void onSocketConnected() {
                        System.out.println("[CLIENT] Websocket client successfully connected");
                    }

                    @Override
                    public void onSocketClosed() {
                        System.out.println("[CLIENT] Websocket client disconnected");
                    }

                    @Override
                    public void onIncomingMessageReceived(byte[] data,
                            IWebsocketClientChannel channel) {
                        System.out.println("[CLIENT] Received message from server : "+ new String(data));
                    }
                });

Websocket client can be enabled with SSL :

// set SSL encryption
clientSocket.setSsl(true);

// set ssl parameters

clientSocket.setSSLParams(KEYSTORE_DEFAULT_TYPE, TRUSTORE_DEFAULT_TYPE,
        CLIENT_KEYSTORE_FILE_PATH, CLIENT_TRUSTORE_FILE_PATH,
        SSL_PROTOCOL, KEYSTORE_PASSWORD, TRUSTORE_PASSWORD);

exactly the same as websocket server

Keystore : public and private server certificates

openssl pkcs12 -export -out server.p12 -inkey server.key -in server.crt

Thus, you will have : String KEYSTORE_DEFAULT_TYPE = "PKCS12"

You have to know your alias (name matching your cert entry), if you dont have it retrieve it with : keytool -v -list -storetype pkcs12 -keystore server.p12

keytool -importkeystore -srckeystore server.p12 -srcstoretype PKCS12 -deststoretype JKS -destkeystore server.jks

Thus, you will have : String KEYSTORE_DEFAULT_TYPE = "JKS"

Trustore : should contain only CA certificates

convert ca cert to jks :

keytool -import -alias ca -file ca.crt -keystore cacerts.jks -storepass 123456

Thus, you will have : String TRUSTORE_DEFAULT_TYPE = "JKS"

TroubleShooting

Bad certificate | Unknown CA errors

This could mean you didn't import your not-trusted-CA certificate into your browser.

The remote host closed the connection

Usually happen when your browser closed the connection before the end of SSL handshake. If you already added your CA to your browser dont worry. Both Chrome and Firefox need to MANUALLY add the certificate (in a popup) so putting it in parameter menu don't change anything.

Just load your URL with "https" : https://127.0.0.1:8443 . Browser will prompt you to accept the certificates and it will probably solve your connection error.

CKR_DOMAIN_PARAMS_INVALID error using openjdk

With openjdk-6-jdk and openjdk-7-jdk, I encountered java.security bug described in https://bugs.launchpad.net/ubuntu/+source/openjdk-7/+bug/1006776 triggering a CKR_DOMAIN_PARAMS_INVALID exception error. Solution was to edit java.security parameters in /etc/java-7-openjdk/security/java.security

I replaced that : 

security.provider.9=sun.security.smartcardio.SunPCSC
security.provider.10=sun.security.pkcs11.SunPKCS11 ${java.home}/lib/security/nss.cfg

with that : 

#security.provider.9=sun.security.smartcardio.SunPCSC
security.provider.9=sun.security.ec.SunEC
#security.provider.10=sun.security.pkcs11.SunPKCS11 ${java.home}/lib/security/nss.cfg

Browser tested

This has been tested on following browser :

Debugging SSL connection error

I recommmend using openssl command line tool to debug ssl connection :

openssl s_client -connect 127.0.0.1:8443

You can also use vm argument debugging java ssl implementation : -Djavax.net.debug=ssl

Server-Client key/cert generation

Certs are in libwesocket-test/certs folder, you will find server,client and ca cert build with easy-rsa :

https://github.com/OpenVPN/easy-rsa

With last release of easy-rsa, you can build your own key with the following :

How to close my websocket server ?

server.closeServer();

COMMAND LINE SYNTAX

The following will open a websocket on port 4343 (default port value for my exemple)

java -cp ../libs/commons-codec-1.9.jar:../libs/http-endec-1.0.jar:libwebsocket-1.0.jar fr.bmartel.websocket.LaunchServer

You can change port number by specifying yours

java -cp ../libs/commons-codec-1.9.jar:../libs/http-endec-1.0.jar:libwebsocket-1.0.jar fr.bmartel.websocket.LaunchServer 4343

This exemple is launched from /release folder

Exemple with Javascript Client

=> You have now a complete websocket chat between java server <-> javascript client in websocket

client side

server side

Exemple with Java websocket client <-> Java websocket server

This will launch one websocket server on 127.0.0.1:8443 and connect a websocket client to it. You will be able to send message to the server via websocket and server will answer you back :

wesocket client exemple

Soon : an exemple using this lib as websocket client communicating with a cpp server
Soon : websocket client exemple