Index: /src/protocol/http/org/apache/jmeter/protocol/http/proxy/ProxyControl.java
===================================================================
--- /src/protocol/http/org/apache/jmeter/protocol/http/proxy/ProxyControl.java	(revision 734176)
+++ /src/protocol/http/org/apache/jmeter/protocol/http/proxy/ProxyControl.java	(working copy)
@@ -156,6 +156,14 @@
     private boolean samplerDownloadImages;
 
     private boolean regexMatch = false;// Should we match using regexes?
+    
+    /*
+     * Is JMeter running in Gui mode? 
+     * Set by org.apache.jmeter.protocol.http.proxy.gui.ProxyControlGui
+     */
+    private boolean inGuiMode = false;
+    
+    
 
     /**
      * Tree node where the samples should be stored.
@@ -955,4 +963,18 @@
     public boolean canRemove() {
         return null == server;
     }
+    
+	/**
+	 * @return the inGuiMode
+	 */
+	public boolean isInGuiMode() {
+		return inGuiMode;
+	}
+
+	/**
+	 * @param inGuiMode the inGuiMode to set
+	 */
+	public void setInGuiMode(boolean inGuiMode) {
+		this.inGuiMode = inGuiMode;
+	}
 }
Index: /src/protocol/http/org/apache/jmeter/protocol/http/proxy/Daemon.java
===================================================================
--- /src/protocol/http/org/apache/jmeter/protocol/http/proxy/Daemon.java	(revision 734176)
+++ /src/protocol/http/org/apache/jmeter/protocol/http/proxy/Daemon.java	(working copy)
@@ -19,12 +19,15 @@
 package org.apache.jmeter.protocol.http.proxy;
 
 import java.io.InterruptedIOException;
+import java.net.BindException;
 import java.net.ServerSocket;
 import java.net.Socket;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.Map;
 
+import javax.swing.JOptionPane;
+
 import org.apache.jorphan.logging.LoggingManager;
 import org.apache.jorphan.util.JOrphanUtils;
 import org.apache.log.Logger;
@@ -153,6 +156,16 @@
                 }
             }
             log.info("Proxy Server stopped");
+            
+        } catch(BindException e){
+        	// daemon port already in use
+        	log.warn("Proxy Server stopped", e);
+        	log.error("Port " + daemonPort + " already in use. Choose a different one for the proxy.");
+       
+        	//TODO: alert in console mode, too
+        	if(target.isInGuiMode()){
+        		JOptionPane.showMessageDialog(null, "Port " + daemonPort + " already in use. Choose a different one for the proxy.", "Proxy Server Port", JOptionPane.ERROR_MESSAGE);
+        	}
         } catch (Exception e) {
             log.warn("Proxy Server stopped", e);
         } finally {
Index: /src/protocol/http/org/apache/jmeter/protocol/http/proxy/gui/ProxyControlGui.java
===================================================================
--- /src/protocol/http/org/apache/jmeter/protocol/http/proxy/gui/ProxyControlGui.java	(revision 734176)
+++ /src/protocol/http/org/apache/jmeter/protocol/http/proxy/gui/ProxyControlGui.java	(working copy)
@@ -196,6 +196,7 @@
     public TestElement createTestElement() {
         model = makeProxyControl();
         log.debug("creating/configuring model = " + model);
+        model.setInGuiMode(true);
         modifyTestElement(model);
         return model;
     }
@@ -220,6 +221,7 @@
         configureTestElement(el);
         if (el instanceof ProxyControl) {
             model = (ProxyControl) el;
+            model.setInGuiMode(true);
             model.setPort(portField.getText());
             setIncludeListInProxyControl(model);
             setExcludeListInProxyControl(model);
@@ -371,6 +373,7 @@
         modifyTestElement(model);
         try {
             replacer.replaceValues(model);
+            model.setInGuiMode(true);
             model.startProxy();
             start.setEnabled(false);
             stop.setEnabled(true);