Add some comment for UDP client

Change-Id: I1be404decbab1a9d8778fb6cc783a2ed44114acd

Author: mengli

src/main/com/danga/MemCached/MemCachedClient.java

@@ -289,8 +289,8 @@ public boolean isUseBinaryProtocol() {
 	 * used when you want to create a ASCIIClient/BinaryClient/UDPASCIIClient
 	 * instance
 	 */
-	protected MemCachedClient(String a, String b) {
-		client = null;
+	protected MemCachedClient(MemCachedClient client) {
+		this.client = client;
 	}
 
 	/**

src/main/com/schooner/MemCached/AscIIClient.java

@@ -53,7 +53,8 @@
 /**
  * This client implements the text protocol of memcached in a very high
  * performance way.<br>
- * Please use the wrapper class {@link MemCachedClient2} for accessing the
+ * <br>
+ * Please use the wrapper class {@link MemCachedClient} for accessing the
  * memcached server.
  * 
  * @author Xingen Wang
@@ -99,13 +100,13 @@ public AscIIClient() {
 	 *            whether use binary protocol.
 	 */
 	public AscIIClient(String poolName) {
-		super("a", "b");
+		super((MemCachedClient) null);
 		this.poolName = poolName;
 		init();
 	}
 
 	public AscIIClient(String poolName, ClassLoader cl, ErrorHandler eh) {
-		super("a", "b");
+		super((MemCachedClient) null);
 		this.poolName = poolName;
 		this.classLoader = cl;
 		this.errorHandler = eh;

src/main/com/schooner/MemCached/AscIIUDPClient.java

@@ -47,10 +47,23 @@
 import com.schooner.MemCached.command.SyncCommand;
 
 /**
- * This client implements the text protocol of memcached in a very high
+ * This client implements the UDP protocol of memcached in a very high
  * performance way.<br>
- * Please use the wrapper class {@link MemCachedClient2} for accessing the
- * memcached server.
+ * <br>
+ * Please use the wrapper class {@link MemCachedClient} for accessing the
+ * memcached server.<br>
+ * <br>
+ * 
+ * When you are using memcached UDP protocol, pay attention that the data size
+ * limit is about 64K due to the datagram length limit of UDP protocol.<br>
+ * <br>
+ * 
+ * A UDP datagram length field specifies the length in bytes of the entire
+ * datagram: header and data. The minimum length is 8 bytes since that's the
+ * length of the header. The field size sets a theoretical limit of 65,535 bytes
+ * (8 byte header + 65,527 bytes of data) for a UDP datagram. The practical
+ * limit for the data length which is imposed by the underlying IPv4 protocol is
+ * 65,507 bytes (65,535 − 8 byte UDP header − 20 byte IP header).
  * 
  * @author Xingen Wang
  * @since 2.5.0

src/main/com/schooner/MemCached/BinaryClient.java

@@ -53,7 +53,8 @@
 /**
  * This client implements the binary protocol of memcached in a very high
  * performance way.<br>
- * Please use the wrapper class {@link MemCachedClient2} for accessing the
+ * <br>
+ * Please use the wrapper class {@link MemCachedClient} for accessing the
  * memcached server.
  * 
  * @author Xingen Wang
@@ -102,7 +103,7 @@ public BinaryClient(String poolName) {
 	}
 
 	public BinaryClient(String poolName, ClassLoader cl, ErrorHandler eh) {
-		super("a", "b");
+		super((MemCachedClient) null);
 		this.poolName = poolName;
 		this.classLoader = cl;
 		this.errorHandler = eh;