add server pinger

src/main/java/cc.fascinated/common/Tuple.java

@@ -0,0 +1,18 @@
+package cc.fascinated.common;
+
+import lombok.AllArgsConstructor;
+import lombok.Getter;
+
+@Getter @AllArgsConstructor
+public class Tuple<L, R> {
+
+    /**
+     * The left value of the tuple.
+     */
+    private final L left;
+
+    /**
+     * The right value of the tuple.
+     */
+    private final R right;
+}