что-то ещё сделал

src/com/company/Client.java

@@ -9,8 +9,8 @@ import java.util.Scanner;
 
 public class Client extends Thread {
     private Socket socket;
-    private ObjectInputStream inputStream;
-    private ObjectOutputStream outputStream;
+    public ObjectInputStream inputStream;
+    public ObjectOutputStream outputStream;
     // Список всех подключенных слиентов
     private List<Client> clientList;
 

src/com/company/Main.java

@@ -5,12 +5,15 @@ import java.net.ServerSocket;
 import java.net.Socket;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Scanner;
 
 public class Main {
+    private static List<Client> clients = new ArrayList<>();
 
     public static void main(String[] args) {
 
-        List<Client> clients = new ArrayList<>();
+        AdminWrite adminWrite = new AdminWrite();
+        adminWrite.start();
 
         try {
             ServerSocket ss = new ServerSocket(9125);
@@ -32,4 +35,26 @@ public class Main {
         }
     }
 
+    private static class AdminWrite extends Thread {
+        @Override
+        public void run() {
+            Scanner scanner = new Scanner(System.in);
+            while (!isInterrupted()) {
+                String message = scanner.nextLine();
+
+                Transport t = new Transport();
+                t.Name = "ADMIN";
+                t.Message = message;
+                for (Client client : clients) {
+                    try {
+                        client.outputStream.writeObject(t);
+                        client.outputStream.flush();
+                    } catch (IOException e) {
+                        e.printStackTrace();
+                    }
+                }
+            }
+        }
+    }
+
 }