diff --git a/pom.xml b/pom.xml
index 5ac5a15..93fe2db 100644
--- a/pom.xml
+++ b/pom.xml
@@ -41,15 +41,6 @@
           <target>1.6</target>
         </configuration>
       </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-javadoc-plugin</artifactId>
-        <version>2.9</version>
-        <configuration>
-          <show>protected</show>
-          <windowtitle>Engine.IO Client API</windowtitle>
-        </configuration>
-      </plugin>
       <plugin>
         <groupId>org.apache.maven.plugins</groupId>
         <artifactId>maven-surefire-plugin</artifactId>
diff --git a/src/main/java/com/github/nkzawa/emitter/Emitter.java b/src/main/java/com/github/nkzawa/emitter/Emitter.java
index 0aa2039..7a65617 100644
--- a/src/main/java/com/github/nkzawa/emitter/Emitter.java
+++ b/src/main/java/com/github/nkzawa/emitter/Emitter.java
@@ -7,6 +7,12 @@ import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.ConcurrentLinkedQueue;
 import java.util.concurrent.ConcurrentMap;
 
+
+/**
+ * The event emitter which is ported from the JavaScript module.
+ *
+ * @see <a href="https://github.com/component/emitter">https://github.com/component/emitter</a>
+ */
 public class Emitter {
 
     private ConcurrentMap<String, ConcurrentLinkedQueue<Listener>> callbacks
@@ -15,6 +21,12 @@ public class Emitter {
     private ConcurrentMap<Listener, Listener> onceCallbacks = new ConcurrentHashMap<Listener, Listener>();
 
 
+    /**
+     * Listens on the event.
+     * @param event event name.
+     * @param fn
+     * @return a reference to to this object.
+     */
     public Emitter on(String event, Listener fn) {
         ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.get(event);
         if (callbacks == null) {
@@ -28,6 +40,13 @@ public class Emitter {
         return this;
     }
 
+    /**
+     * Adds a one time listener for the event.
+     *
+     * @param event
+     * @param fn
+     * @return a reference to to this object.
+     */
     public Emitter once(final String event, final Listener fn) {
         Listener on = new Listener() {
             @Override
@@ -42,12 +61,23 @@ public class Emitter {
         return this;
     }
 
+    /**
+     * Removes all registered listeners.
+     *
+     * @return a reference to to this object.
+     */
     public Emitter off() {
         this.callbacks.clear();
         this.onceCallbacks.clear();
         return this;
     }
 
+    /**
+     * Removes all listeners of the specified event.
+     *
+     * @param event
+     * @return a reference to to this object.
+     */
     public Emitter off(String event) {
         ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.remove(event);
         if (callbacks != null) {
@@ -58,6 +88,13 @@ public class Emitter {
         return this;
     }
 
+    /**
+     * Removes the listener.
+     *
+     * @param event
+     * @param fn
+     * @return a reference to to this object.
+     */
     public Emitter off(String event, Listener fn) {
         ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.get(event);
         if (callbacks != null) {
@@ -67,6 +104,13 @@ public class Emitter {
         return this;
     }
 
+    /**
+     * Executes each of listeners with the given args.
+     *
+     * @param event
+     * @param args
+     * @return a reference to to this object.
+     */
     public Emitter emit(String event, Object... args) {
         ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.get(event);
         if (callbacks != null) {
@@ -78,12 +122,24 @@ public class Emitter {
         return this;
     }
 
+    /**
+     * Returns a list of listeners for the specified event.
+     *
+     * @param event
+     * @return a reference to to this object.
+     */
     public List<Listener> listeners(String event) {
         ConcurrentLinkedQueue<Listener> callbacks = this.callbacks.get(event);
         return callbacks != null ?
                 new ArrayList<Listener>(callbacks) : new ArrayList<Listener>();
     }
 
+    /**
+     * Check if this emitter has listeners for the specified event.
+     *
+     * @param event
+     * @return a reference to to this object.
+     */
     public boolean hasListeners(String event) {
         return !this.listeners(event).isEmpty();
     }
diff --git a/src/main/java/com/github/nkzawa/engineio/client/Socket.java b/src/main/java/com/github/nkzawa/engineio/client/Socket.java
index 1971437..2e6ea65 100644
--- a/src/main/java/com/github/nkzawa/engineio/client/Socket.java
+++ b/src/main/java/com/github/nkzawa/engineio/client/Socket.java
@@ -15,6 +15,12 @@ import java.util.*;
 import java.util.concurrent.*;
 import java.util.logging.Logger;
 
+
+/**
+ * The socket class for Event.IO Client.
+ *
+ * @see <a href="https://github.com/LearnBoost/engine.io-client">https://github.com/LearnBoost/engine.io-client</a>
+ */
 public abstract class Socket extends Emitter {
 
     private static final Logger logger = Logger.getLogger(Socket.class.getName());
@@ -32,8 +38,36 @@ public abstract class Socket extends Emitter {
         put(CLOSED, "closed");
     }};
 
+    /**
+     * Called on successful connection.
+     */
     public static final String EVENT_OPEN = "open";
+
+    /**
+     * Called on disconnection.
+     */
     public static final String EVENT_CLOSE = "close";
+
+    /**
+     * Called when data is received from the server.
+     */
+    public static final String EVENT_MESSAGE = "message";
+
+    /**
+     * Called when an error occurs.
+     */
+    public static final String EVENT_ERROR = "error";
+
+    /**
+     * Called on completing a buffer flush.
+     */
+    public static final String EVENT_FLUSH = "flush";
+
+    /**
+     * Called after `drain` event of transport if writeBuffer is empty.
+     */
+    public static final String EVENT_DRAIN = "drain";
+
     public static final String EVENT_HANDSHAKE = "handshake";
     public static final String EVENT_UPGRADING = "upgrading";
     public static final String EVENT_UPGRADE = "upgrade";
@@ -41,17 +75,20 @@ public abstract class Socket extends Emitter {
     public static final String EVENT_PACKET_CREATE = "packetCreate";
     public static final String EVENT_HEARTBEAT = "heartbeat";
     public static final String EVENT_DATA = "data";
-    public static final String EVENT_MESSAGE = "message";
-    public static final String EVENT_ERROR = "error";
-    public static final String EVENT_DRAIN = "drain";
-    public static final String EVENT_FLUSH = "flush";
 
     private static final Runnable noop = new Runnable() {
         @Override
         public void run() {}
     };
 
+    /**
+     * List of Socket instances.
+     */
     public static final Sockets sockets = new Sockets();
+
+    /**
+     * The protocol version.
+     */
     public static final int protocol = Parser.protocol;
 
     private boolean secure;
@@ -80,6 +117,12 @@ public abstract class Socket extends Emitter {
     private ScheduledExecutorService heartbeatScheduler = Executors.newSingleThreadScheduledExecutor();
 
 
+    /**
+     * Creates a socket.
+     *
+     * @param uri URI to connect.
+     * @throws URISyntaxException
+     */
     public Socket(String uri) throws URISyntaxException {
         this(uri, null);
     }
@@ -88,6 +131,13 @@ public abstract class Socket extends Emitter {
         this(uri, null);
     }
 
+    /**
+     * Creates a socket with options.
+     *
+     * @param uri URI to connect.
+     * @param opts options for socket
+     * @throws URISyntaxException
+     */
     public Socket(String uri, Options opts) throws URISyntaxException {
         this(new URI(uri), opts);
     }
@@ -115,13 +165,16 @@ public abstract class Socket extends Emitter {
         this.timestampParam = opts.timestampParam != null ? opts.timestampParam : "t";
         this.timestampRequests = opts.timestampRequests;
         this.transports = new ArrayList<String>(Arrays.asList(opts.transports != null ?
-                opts.transports : new String[] {Polling.NAME, WebSocket.NAME}));
+                opts.transports : new String[]{Polling.NAME, WebSocket.NAME}));
         this.policyPort = opts.policyPort != 0 ? opts.policyPort : 843;
 
         Socket.sockets.add(this);
         Socket.sockets.evs.emit(Sockets.EVENT_ADD, this);
     }
 
+    /**
+     * Connects the client.
+     */
     public void open() {
         this.readyState = OPENING;
         Transport transport = this.createTransport(this.transports.get(0));
@@ -434,10 +487,21 @@ public abstract class Socket extends Emitter {
         this.send(msg, fn);
     }
 
+    /**
+     * Sends a message.
+     *
+     * @param msg
+     */
     public void send(String msg) {
         this.send(msg, null);
     }
 
+    /**
+     * Sends a message.
+     *
+     * @param msg
+     * @param fn callback to be called on drain
+     */
     public void send(String msg, Runnable fn) {
         this.sendPacket(Packet.MESSAGE, msg, fn);
     }
@@ -459,6 +523,11 @@ public abstract class Socket extends Emitter {
         this.flush();
     }
 
+    /**
+     * Disconnects the client.
+     *
+     * @return a reference to to this object.
+     */
     public Socket close() {
         if (this.readyState == OPENING || this.readyState == OPEN) {
             this.onClose("forced close");
@@ -524,10 +593,18 @@ public abstract class Socket extends Emitter {
 
     public static class Options extends Transport.Options {
 
+        /**
+         * List of transport names.
+         */
+        public String[] transports;
+
+        /**
+         * Whether to upgrade the transport. Defaults to `true`.
+         */
+        public boolean upgrade = true;
+
         public String host;
         public String query;
-        public String[] transports;
-        public boolean upgrade = true;
 
 
         private static Options fromURI(URI uri, Options opts) {