enable to send cookie

src/main/java/com/github/nkzawa/engineio/client/Socket.java

@@ -102,6 +102,7 @@ public abstract class Socket extends Emitter {
     private String hostname;
     private String path;
     private String timestampParam;
+    private String cookie;
     private List<String> transports;
     private List<String> upgrades;
     private Map<String, String> query;
@@ -165,6 +166,7 @@ public abstract class Socket extends Emitter {
         this.transports = new ArrayList<String>(Arrays.asList(opts.transports != null ?
                 opts.transports : new String[]{Polling.NAME, WebSocket.NAME}));
         this.policyPort = opts.policyPort != 0 ? opts.policyPort : 843;
+        this.cookie = opts.cookie;
 
         Socket.sockets.add(this);
         Socket.sockets.evs.emit(Sockets.EVENT_ADD, this);
@@ -204,6 +206,7 @@ public abstract class Socket extends Emitter {
         opts.timestampRequests = this.timestampRequests;
         opts.timestampParam = this.timestampParam;
         opts.policyPort = this.policyPort;
+        opts.cookie = this.cookie;
 
         if (WebSocket.NAME.equals(name)) {
             return new WebSocket(opts);

src/main/java/com/github/nkzawa/engineio/client/Transport.java

@@ -121,6 +121,11 @@ public abstract class Transport extends Emitter {
 
     public static class Options {
 
+        /**
+         * Cookie value for handshake.
+         */
+        public String cookie;
+
         public String hostname;
         public String path;
         public String timestampParam;

src/main/java/com/github/nkzawa/engineio/client/transports/PollingXHR.java

@@ -17,9 +17,11 @@ public class PollingXHR extends Polling {
 
     private Request sendXhr;
     private Request pollXhr;
+    private String cookie;
 
     public PollingXHR(Options opts) {
         super(opts);
+        this.cookie = opts.cookie;
     }
 
     protected Request request() {
@@ -31,6 +33,7 @@ public class PollingXHR extends Polling {
             opts = new Request.Options();
         }
         opts.uri = this.uri();
+        opts.cookie = this.cookie;
         return new Request(opts);
     }
 
@@ -110,12 +113,14 @@ public class PollingXHR extends Polling {
         String method;
         String uri;
         String data;
+        String cookie;
         HttpURLConnection xhr;
 
         public Request(Options opts) {
             this.method = opts.method != null ? opts.method : "GET";
             this.uri = opts.uri;
             this.data = opts.data;
+            this.cookie = opts.cookie;
         }
 
         public void create() {
@@ -134,6 +139,10 @@ public class PollingXHR extends Polling {
                 xhr.setRequestProperty("Content-type", "text/plain;charset=UTF-8");
             }
 
+            if (this.cookie != null) {
+                xhr.setRequestProperty("Cookie", this.cookie);
+            }
+
             logger.fine(String.format("sending xhr with url %s | data %s", this.uri, this.data));
             xhrService.submit(new Runnable() {
                 @Override
@@ -201,6 +210,7 @@ public class PollingXHR extends Polling {
             public String uri;
             public String method;
             public String data;
+            public String cookie;
         }
     }
 }