Assign ID to message

src/main/java/dslab/Message.java

@@ -11,6 +11,7 @@ public class Message {
     private Email from;
     private String subject;
     private String data;
+    private Integer id;
 
     public Message() {
     }
@@ -71,6 +72,14 @@ public class Message {
         this.data = data;
     }
 
+    public Integer getId() {
+        return id;
+    }
+
+    public void setId(Integer id) {
+        this.id = id;
+    }
+
     @Override
     public String toString() {
         return "from " + getFrom().toString() + "\n" +

src/main/java/dslab/mailbox/DMTPConnection.java

@@ -110,6 +110,7 @@ public class DMTPConnection implements Runnable {
 
     private synchronized void storeMessage() throws UnknownRecipientException {
         logger.info("Storing message " + msg.toString());
+        this.msg.setId(MailboxServer.id++);
         String errorUnknownRecipient = "";
         for (Email recipient : this.msg.getTo()) {
             if (this.messageStorage.containsKey(recipient)) {

src/main/java/dslab/mailbox/MailboxServer.java

@@ -29,6 +29,8 @@ public class MailboxServer implements IMailboxServer, Runnable {
     private final ConcurrentHashMap<Email, LinkedList<Message>> messageStorage = new ConcurrentHashMap<>();
     private final ConcurrentHashMap<String, String> userStorage = new ConcurrentHashMap<>();
 
+    public static volatile Integer id;
+
     /**
      * Creates a new server instance.
      *
@@ -51,6 +53,8 @@ public class MailboxServer implements IMailboxServer, Runnable {
             messageStorage.put(current, new LinkedList<>());
         }
 
+        id = 0;
+
         this.shell = new Shell(in, out);
         this.shell.register(this);
         this.shell.setPrompt("Mailboxserver> ");
@@ -78,7 +82,6 @@ public class MailboxServer implements IMailboxServer, Runnable {
     @Command
     @Override
     public void shutdown() {
-        // TODO shutdown DMTPListener
         // TODO shutdown DMAPListener
         try {
             if (dmtpServerSocket != null)