fixes #1701 simple connection pool ports from the 1.6.x (#1702)

Co-authored-by: miklish <michael.n.christoff@gmail.com>

client/src/main/java/com/networknt/client/simplepool/SimpleConnection.java

@@ -0,0 +1,61 @@
+/*
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * @author miklish Michael N. Christoff
+ *
+ * testing / QA
+ *   AkashWorkGit
+ *   jaydeepparekh1311
+ */
+
+package com.networknt.client.simplepool;
+
+/***
+ * SimpleConnection is an interface that contains all the required functions and properties of
+ * a connection that are needed by the SimpleConnectionHolder, SimpleURIConnectionPool, and
+ * SimpleConnectionPool classes.
+ *
+ * Concrete HTTP network connections (like Undertow's ClientConnection class) should be wrapped in
+ * classes that implement the SimpleConnection interface.
+ *
+ */
+public interface SimpleConnection {
+    /**
+     * Tells whether or not the connection is open
+     * @return returns true iff the raw connection is open
+     */
+    public boolean isOpen();
+
+    /**
+     * Returns the raw connection object. This must always be non-null
+     * @return returns the raw connection object
+     */
+    public Object getRawConnection();
+
+    /**
+     * Tells whether the connection supports HTTP/2 connection multiplexing
+     * @return returns true iff the connection supports HTTP/2 connection multiplexing
+     */
+    public boolean isMultiplexingSupported();
+
+    /**
+     * Returns the client side address of the connection
+     * @return the client side address of the connection
+     */
+    public String getLocalAddress();
+
+    /**
+     * Safely closes the connection
+     */
+    public void safeClose();
+}