diff --git a/src/com/annimon/socketfiletransfer/operations/CursorOperation.java b/src/com/annimon/socketfiletransfer/operations/CursorOperation.java
index dc8830c..f2d5fba 100644
--- a/src/com/annimon/socketfiletransfer/operations/CursorOperation.java
+++ b/src/com/annimon/socketfiletransfer/operations/CursorOperation.java
@@ -22,7 +22,7 @@ import javax.swing.JPanel;
  * Управление курсором.
  * @author aNNiMON
  */
-public class CursorOperation implements Operation {
+public class CursorOperation extends Operation {
     
     private static final int
             NONE = -1,
@@ -33,9 +33,6 @@ public class CursorOperation implements Operation {
             TYPE_KEY_RELEASED = 5,
             STOP = 10;
     
-    private DataInputStream dis;
-    private DataOutputStream dos;
-    
     private RobotUtils robot;
     private boolean running;
     
diff --git a/src/com/annimon/socketfiletransfer/operations/FileOperation.java b/src/com/annimon/socketfiletransfer/operations/FileOperation.java
index 8276178..19661c1 100644
--- a/src/com/annimon/socketfiletransfer/operations/FileOperation.java
+++ b/src/com/annimon/socketfiletransfer/operations/FileOperation.java
@@ -14,13 +14,10 @@ import java.io.IOException;
  *
  * @author aNNiMON
  */
-public class FileOperation implements Operation {
+public class FileOperation extends Operation {
     
     private static final int BUFFER_SIZE = 1024;
     
-    private DataInputStream dis;
-    private DataOutputStream dos;
-    
     public FileOperation(DataInputStream dis) {
         this.dis = dis;
     }
diff --git a/src/com/annimon/socketfiletransfer/operations/MessageOperation.java b/src/com/annimon/socketfiletransfer/operations/MessageOperation.java
index cedd161..ffc8b43 100644
--- a/src/com/annimon/socketfiletransfer/operations/MessageOperation.java
+++ b/src/com/annimon/socketfiletransfer/operations/MessageOperation.java
@@ -10,10 +10,7 @@ import java.io.IOException;
  *
  * @author aNNiMON
  */
-public class MessageOperation implements Operation {
-    
-    private DataInputStream dis;
-    private DataOutputStream dos;
+public class MessageOperation extends Operation {
     
     public MessageOperation(DataInputStream dis) {
         this.dis = dis;
diff --git a/src/com/annimon/socketfiletransfer/operations/Operation.java b/src/com/annimon/socketfiletransfer/operations/Operation.java
index 09afb04..58764ed 100644
--- a/src/com/annimon/socketfiletransfer/operations/Operation.java
+++ b/src/com/annimon/socketfiletransfer/operations/Operation.java
@@ -1,13 +1,19 @@
 package com.annimon.socketfiletransfer.operations;
 
+import java.io.DataInputStream;
+import java.io.DataOutputStream;
+
 /**
  *
  * @author aNNiMON
  */
-public interface Operation {
+public abstract class Operation {
     
-    void startServerSide() throws Exception;
+    protected DataInputStream dis;
+    protected DataOutputStream dos;
     
-    void startClientSide(Object... params) throws Exception;
+    public abstract void startServerSide() throws Exception;
+    
+    public abstract void startClientSide(Object... params) throws Exception;
 
 }