diff --git a/pom.xml b/pom.xml
index e067050..8d7b185 100644
--- a/pom.xml
+++ b/pom.xml
@@ -58,6 +58,12 @@
       <version>${junit-jupiter.version}</version>
       <scope>test</scope>
     </dependency>
+    <dependency>
+  <groupId>io.netty</groupId>
+  <artifactId>netty-tcnative-boringssl-static</artifactId>
+  <version>2.0.59.Final</version>
+  </dependency>
+
   </dependencies>
 
   <build>
diff --git a/src/main/java/cx/lehmann/gemini/gemini/MainVerticle.java b/src/main/java/cx/lehmann/gemini/gemini/MainVerticle.java
index 6df4970..89b9404 100644
--- a/src/main/java/cx/lehmann/gemini/gemini/MainVerticle.java
+++ b/src/main/java/cx/lehmann/gemini/gemini/MainVerticle.java
@@ -1,8 +1,15 @@
 package cx.lehmann.gemini.gemini;
 
+import java.security.cert.Certificate;
+import java.util.List;
+
+import javax.net.ssl.SSLPeerUnverifiedException;
+
 import io.vertx.core.AbstractVerticle;
 import io.vertx.core.Promise;
+import io.vertx.core.http.ClientAuth;
 import io.vertx.core.net.NetServerOptions;
+//import io.vertx.core.net.OpenSSLEngineOptions;
 import io.vertx.core.net.PemKeyCertOptions;
 
 public class MainVerticle extends AbstractVerticle {
@@ -16,26 +23,30 @@ public class MainVerticle extends AbstractVerticle {
     options.setPemKeyCertOptions(new PemKeyCertOptions()
         .setCertPath(certPath)
         .setKeyPath(certPath))
-    .setSsl(true);
-//    .setClientAuth(ClientAuth.REQUEST);
+    .setSsl(true)
+//    .setOpenSslEngineOptions(new OpenSSLEngineOptions())
+    .setClientAuth(ClientAuth.REQUIRED);
 
     vertx.createNetServer(options).connectHandler(conn -> {
       conn.handler(event -> {
+        System.out.println("accepted connection:"+conn.remoteAddress());
         String url=event.toString("UTF-8");
         if(!url.endsWith("\r\n")) {
           conn.write("40 format error\r\n");
           conn.close();
         } else {
           url=url.substring(0, url.length()-2);
+//          conn.write("60 cert required\r\n");
           conn.write("20 text/gemini\r\n");
-          conn.write(url);
+          conn.write("url:"+url);
           conn.write("\n");
-//          try {
-//            conn.write(conn.peerCertificates().toString());
-//          } catch (SSLPeerUnverifiedException ex) {
-//            // TODO Auto-generated catch block
-//            ex.printStackTrace();
-//          }
+          try {
+            List<Certificate> certs=conn.peerCertificates();
+            System.out.println("get certs");
+            conn.write(certs.toString());
+          } catch (SSLPeerUnverifiedException ex) {
+            ex.printStackTrace();
+          }
           conn.close();
         }
       }