diff --git a/src/main/java/envoy/client/Client.java b/src/main/java/envoy/client/Client.java
index 51ee5c0..53a7865 100644
--- a/src/main/java/envoy/client/Client.java
+++ b/src/main/java/envoy/client/Client.java
@@ -36,7 +36,7 @@ public class Client {
 	private ObjectFactory	objectFactory	= new ObjectFactory();
 	private DatatypeFactory	datatypeFactory;
 	private Config			config;
-	private User user;
+	private User			user;
 
 	public Client(Config config, String username) {
 		this.config = config;
@@ -54,9 +54,9 @@ public class Client {
 	 * Because sending a request is a blocking operation, it is executed
 	 * asynchronously.
 	 * 
-	 * @param sender      Name of the sender
-	 * @param recipient   Name of the recipient
-	 * @param textContent Content (text) of the message
+	 * @param sender      name of the sender
+	 * @param recipient   name of the recipient
+	 * @param textContent content (text) of the message
 	 */
 	public void sendMessage(Message message) {
 		new Thread(() -> {
@@ -92,7 +92,7 @@ public class Client {
 	 * @param senderID    The ID of the sender
 	 * @param recipientID The ID of the recipient
 	 * @param textContent The content (text) of the message
-	 * @return Prepared {@link Message} object
+	 * @return prepared {@link Message} object
 	 */
 	public Message createMessage(long senderID, long recipientID, String textContent) {
 		Message.MetaData metaData = objectFactory.createMessageMetaData();
@@ -129,18 +129,18 @@ public class Client {
 		client.close();
 		return users;
 	}
-	
+
 	/**
-	 * Returns the user by name.
+	 * Returns a {@link User} with a specific name by name.
 	 * 
-	 * @param name - the name of the user
-	 * @return an user object
+	 * @param name - the name of the {@link User}
+	 * @return a {@link User} with the specified name
 	 * @since Envoy 0.1
 	 */
 	private User getUser(String name) {
 		javax.ws.rs.client.Client	client		= ClientBuilder.newClient();
-		WebTarget					target		= client
-			.target(String.format("%s:%d/envoy-server/rest/user/sender?name=" + name, config.getServer(), config.getPort()));
+		WebTarget					target		= client.target(String
+			.format("%s:%d/envoy-server/rest/user/sender?name=" + name, config.getServer(), config.getPort()));
 		Response					response	= target.request("application/xml").get();
 		Users						users		= response.readEntity(Users.class);
 		System.out.println("Response code: " + response.getStatus());
@@ -148,4 +148,10 @@ public class Client {
 		client.close();
 		return users.getUser().get(0);
 	}
+
+	/**
+	 * @return the user id of this client
+	 * @since Envoy 0.1
+	 */
+	public long getSenderID() { return user.getID(); }
 }
\ No newline at end of file
diff --git a/src/main/java/envoy/client/ui/ChatWindow.java b/src/main/java/envoy/client/ui/ChatWindow.java
index 8f71776..0e9bc40 100644
--- a/src/main/java/envoy/client/ui/ChatWindow.java
+++ b/src/main/java/envoy/client/ui/ChatWindow.java
@@ -2,13 +2,10 @@ package envoy.client.ui;
 
 import java.awt.Color;
 import java.awt.ComponentOrientation;
-import java.awt.EventQueue;
 import java.awt.Font;
 import java.awt.GridBagConstraints;
 import java.awt.GridBagLayout;
 import java.awt.Insets;
-import java.io.IOException;
-import java.util.Properties;
 
 import javax.swing.DefaultListModel;
 import javax.swing.JButton;
@@ -23,7 +20,6 @@ import javax.swing.SwingUtilities;
 import javax.swing.border.EmptyBorder;
 
 import envoy.client.Client;
-import envoy.client.Config;
 import envoy.schema.Message;
 import envoy.schema.User;
 import envoy.schema.Users;
@@ -51,7 +47,7 @@ public class ChatWindow extends JFrame {
 
 	public ChatWindow(Client client) {
 		this.client = client;
-		
+
 		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 		setBounds(100, 100, 600, 800);
 		setTitle("Envoy");
@@ -138,7 +134,8 @@ public class ChatWindow extends JFrame {
 
 			// TODO: Acquire proper sender id
 			if (!messageEnterTextfield.getText().isEmpty() && recipientID != 0) try {
-				final Message message = client.createMessage(1, recipientID, messageEnterTextfield.getText());
+				final Message message = client
+					.createMessage(client.getSenderID(), recipientID, messageEnterTextfield.getText());
 				client.sendMessage(message);
 				appendMessageToChat(message);
 				messageEnterTextfield.setText("");
@@ -214,5 +211,4 @@ public class ChatWindow extends JFrame {
 				+ message.getMetaData().getSender() + "</b> </small>" + "<br>" + "<p style=\"color:white\">"
 				+ getFirstTextContent(message) + "</span></html>");
 	}
-
 }
\ No newline at end of file
diff --git a/src/main/java/envoy/client/ui/Startup.java b/src/main/java/envoy/client/ui/Startup.java
index d2848a9..b525861 100644
--- a/src/main/java/envoy/client/ui/Startup.java
+++ b/src/main/java/envoy/client/ui/Startup.java
@@ -5,15 +5,12 @@ import java.io.IOException;
 import java.util.Properties;
 
 import javax.swing.JOptionPane;
-import javax.ws.rs.client.Entity;
-import javax.ws.rs.client.WebTarget;
-import javax.ws.rs.core.Response;
 
 import envoy.client.Client;
 import envoy.client.Config;
 
 /**
- * Starts Envoy and sets a user.
+ * Starts the Envoy client and prompts the user to enter their name.
  * 
  * Project: <strong>envoy-client</strong><br>
  * File: <strong>Startup.java</strong><br>
@@ -24,9 +21,7 @@ import envoy.client.Config;
  * @since Envoy 0.1
  */
 public class Startup {
-	
-	private static String userName;
-	
+
 	public static void main(String[] args) {
 		Config config = new Config();
 		if (args.length > 0) {
@@ -42,15 +37,18 @@ public class Startup {
 			}
 		}
 
-		if(!config.isInitialized()) {
+		if (!config.isInitialized()) {
 			System.err.println("Server or port are not defined. Exiting...");
 			System.exit(1);
 		}
 
-		userName = JOptionPane.showInputDialog("Please enter your username");
-		
+		String userName = JOptionPane.showInputDialog("Please enter your username");
+		if (userName == null || userName.isEmpty()) {
+			System.err.println("User name is not set or empty. Exiting...");
+			System.exit(1);
+		}
 		Client client = new Client(config, userName);
-		
+
 		EventQueue.invokeLater(() -> {
 			try {
 				ChatWindow frame = new ChatWindow(client);
@@ -60,4 +58,4 @@ public class Startup {
 			}
 		});
 	}
-}
+}
\ No newline at end of file