diff --git a/src/java/davmail/AbstractServer.java b/src/java/davmail/AbstractServer.java
index 7bf06a8d..b8c66233 100644
--- a/src/java/davmail/AbstractServer.java
+++ b/src/java/davmail/AbstractServer.java
@@ -15,18 +15,14 @@ public abstract class AbstractServer extends Thread {
      * Create a ServerSocket to listen for connections.
      * Start the thread.
      */
-    public AbstractServer(int port, int defaultPort) {
+    public AbstractServer(int port, int defaultPort) throws IOException {
         if (port == 0) {
             this.port = defaultPort;
         } else {
             this.port = port;
         }
-        try {
-            //noinspection SocketOpenedButNotSafelyClosed
-            serverSocket = new ServerSocket(port);
-        } catch (IOException e) {
-            DavGatewayTray.error("Exception creating server socket", e);
-        }
+        //noinspection SocketOpenedButNotSafelyClosed
+        serverSocket = new ServerSocket(port);
     }
 
 
@@ -74,7 +70,9 @@ public abstract class AbstractServer extends Thread {
 
     public void close() {
         try {
-            serverSocket.close();
+            if (serverSocket != null) {
+                serverSocket.close();
+            }
         } catch (IOException e) {
             DavGatewayTray.warn("Exception closing server socket", e);
         }
diff --git a/src/java/davmail/DavGateway.java b/src/java/davmail/DavGateway.java
index 383f306c..3aa1257f 100644
--- a/src/java/davmail/DavGateway.java
+++ b/src/java/davmail/DavGateway.java
@@ -3,6 +3,8 @@ package davmail;
 import davmail.pop.PopServer;
 import davmail.smtp.SmtpServer;
 
+import java.io.IOException;
+
 /**
  * DavGateway main class
  */
@@ -56,13 +58,18 @@ public class DavGateway {
         if (popPort == 0) {
             popPort = PopServer.DEFAULT_PORT;
         }
-        smtpServer = new SmtpServer(smtpPort);
-        popServer = new PopServer(popPort);
-        smtpServer.start();
-        popServer.start();
 
-        DavGatewayTray.info("DavMail gateway listening on SMTP port " + smtpPort +
-                " and POP port " + popPort);
+        try {
+            smtpServer = new SmtpServer(smtpPort);
+            popServer = new PopServer(popPort);
+            smtpServer.start();
+            popServer.start();
+
+            DavGatewayTray.info("DavMail gateway listening on SMTP port " + smtpPort +
+                    " and POP port " + popPort);
+        } catch (IOException e) {
+            DavGatewayTray.error("Exception creating server socket", e);
+        }
 
     }
 
diff --git a/src/java/davmail/imap/ImapServer.java b/src/java/davmail/imap/ImapServer.java
index ed0be803..6e1004ac 100644
--- a/src/java/davmail/imap/ImapServer.java
+++ b/src/java/davmail/imap/ImapServer.java
@@ -2,6 +2,7 @@ package davmail.imap;
 
 
 import java.net.Socket;
+import java.io.IOException;
 
 import davmail.AbstractServer;
 import davmail.AbstractConnection;
@@ -16,7 +17,7 @@ public class ImapServer extends AbstractServer {
      * Create a ServerSocket to listen for connections.
      * Start the thread.
      */
-    public ImapServer(int port) {
+    public ImapServer(int port) throws IOException {
         super(port, ImapServer.DEFAULT_PORT);
     }
 
diff --git a/src/java/davmail/pop/PopServer.java b/src/java/davmail/pop/PopServer.java
index e5813a51..1c1329e0 100644
--- a/src/java/davmail/pop/PopServer.java
+++ b/src/java/davmail/pop/PopServer.java
@@ -5,6 +5,7 @@ import davmail.AbstractServer;
 import davmail.AbstractConnection;
 
 import java.net.Socket;
+import java.io.IOException;
 
 /**
  * Pop3 server
@@ -17,7 +18,7 @@ public class PopServer extends AbstractServer {
      * Start the thread.
      * @param port pop listen port, 110 if not defined (0)
      */
-    public PopServer(int port) {
+    public PopServer(int port) throws IOException {
         super(port, PopServer.DEFAULT_PORT);
     }
 
diff --git a/src/java/davmail/smtp/SmtpServer.java b/src/java/davmail/smtp/SmtpServer.java
index a8664af9..ff569639 100644
--- a/src/java/davmail/smtp/SmtpServer.java
+++ b/src/java/davmail/smtp/SmtpServer.java
@@ -4,6 +4,7 @@ import davmail.AbstractServer;
 import davmail.AbstractConnection;
 
 import java.net.Socket;
+import java.io.IOException;
 
 public class SmtpServer extends AbstractServer {
     public static final int DEFAULT_PORT = 25;
@@ -12,7 +13,7 @@ public class SmtpServer extends AbstractServer {
      * Create a ServerSocket to listen for connections.
      * Start the thread.
      */
-    public SmtpServer(int port) {
+    public SmtpServer(int port) throws IOException {
         super(port, SmtpServer.DEFAULT_PORT);
     }