Added Leave sendable and requestable.

src/main/java/vslab1/src/Request/Data/ReceivedLeaveNotification.java

@@ -0,0 +1,33 @@
+package vslab1.src.Request.Data;
+
+import vslab1.src.FileReaderWriter.FileReaderWriter;
+import vslab1.src.Peers.EOnlineState;
+import vslab1.src.Peers.Peer;
+import vslab1.src.Sending.SendingQueue;
+import vslab1.src.Sending.Data.EDataType;
+
+/**
+ * Received leave notification and sets peer online state in list to offline.
+ */
+public record ReceivedLeaveNotification(Peer sender, Peer receiver) implements Requestable {
+
+    @Override
+    public EDataType getType() {
+        return EDataType.LeaveNotification;
+    }
+
+    @Override
+    public Peer getSender() {
+        return sender;
+    }
+
+    @Override
+    public Peer getReceiver() {
+        return receiver;
+    }
+
+    @Override
+    public void execute(SendingQueue sendingQueue) {
+        FileReaderWriter.updatePeer(new Peer(sender.ipAddress(), sender.port(), null, EOnlineState.Offline));
+    }
+}

src/main/java/vslab1/src/Sending/Data/LeaveNotification.java

@@ -0,0 +1,33 @@
+package vslab1.src.Sending.Data;
+
+import vslab1.src.Peers.Peer;
+
+/**
+ * Sent to all online peers if this peer goes offline.
+ */
+public record LeaveNotification(Peer sender, Peer receiver) implements Sendable {
+
+    @Override
+    public EDataType getType() {
+        return EDataType.LeaveNotification;
+    }
+
+    @Override
+    public Peer getSender() {
+        return sender;
+    }
+
+    @Override
+    public Peer getReceiver() {
+        return receiver;
+    }
+
+    @Override
+    public byte[] getMessage() {
+        String request =
+            "{\"leave\":\"\"" +
+            "," + 
+            "\"ipPort\":\"" + sender.ipAddress() + ":" + sender.port() + "\"}";
+        return request.getBytes();
+    }
+}