SslSocketClient.java - SSL Client Socket Example

JDK Tutorials - Herong's Tutorial Examples

∟SSL Socket Communication Testing Programs

∟SslSocketClient.java - SSL Client Socket Example

This section provides a tutorial example on how to write a sample program to create a SSL client socket to connect to a SSL server socket. The connection will fail if the server's certificate is self-signed.

Since my SSL socket server does not require client authentication, we can create a SSL socket client with the default SSL socket factory. Here is my sample program, SslSocketClient.java, which can be used to communicate with SslReverseEchoer.java:

/* SslSocketClient.java
 - Copyright (c) 2014, HerongYang.com, All Rights Reserved.
 */
import java.io.*;
import java.net.*;
import javax.net.ssl.*;
public class SslSocketClient {
   public static void main(String[] args) {
      BufferedReader in = new BufferedReader(
         new InputStreamReader(System.in));
      PrintStream out = System.out;
      SSLSocketFactory f = 
         (SSLSocketFactory) SSLSocketFactory.getDefault();
      try {
         SSLSocket c =
           (SSLSocket) f.createSocket("localhost", 8888);
         printSocketInfo(c);
         c.startHandshake();
         BufferedWriter w = new BufferedWriter(
            new OutputStreamWriter(c.getOutputStream()));
         BufferedReader r = new BufferedReader(
            new InputStreamReader(c.getInputStream()));
         String m = null;
         while ((m=r.readLine())!= null) {
            out.println(m);
            m = in.readLine();
            w.write(m,0,m.length());
            w.newLine();
            w.flush();
         }
         w.close();
         r.close();
         c.close();
      } catch (IOException e) {
         System.err.println(e.toString());
      }
   }
   private static void printSocketInfo(SSLSocket s) {
      System.out.println("Socket class: "+s.getClass());
      System.out.println("   Remote address = "
         +s.getInetAddress().toString());
      System.out.println("   Remote port = "+s.getPort());
      System.out.println("   Local socket address = "
         +s.getLocalSocketAddress().toString());
      System.out.println("   Local address = "
         +s.getLocalAddress().toString());
      System.out.println("   Local port = "+s.getLocalPort());
      System.out.println("   Need client authentication = "
         +s.getNeedClientAuth());
      SSLSession ss = s.getSession();
      System.out.println("   Cipher suite = "+ss.getCipherSuite());
      System.out.println("   Protocol = "+ss.getProtocol());
   }
}

Now run this program in a separate window, you will get:

Socket class: class com.sun.net.ssl.internal.ssl.SSLSocketImpl
   Remote address = localhost/127.0.0.1
   Remote port = 8888
   Local socket address = /127.0.0.1:2183
   Local address = /127.0.0.1
   Local port = 2183
   Need client authentication = false
   Cipher suite = SSL_NULL_WITH_NULL_NULL
   Protocol = NONE
javax.net.ssl.SSLException: Connection has been shutdown: 
   javax.net.ssl.SSLHandshakeException: 
   sun.security.validator.ValidatorException: 
      PKIX path building failed: 
   sun.security.provider.certpath.SunCertPathBuilderException: 
      unable to find valid certification path to requested target

Obviously, there is a problem. The TCP/IP layer connection was ok, but the SSL handshake process failed. The error message says that server certificate received has no valid path from any existing certificate authority.

This is an expected error, because the server certificate is a self-signed certificate, not signed by any trusted certificate authorities directly or indirectly. See the next section on how to resolve this problem.

Last update: 2014.

Table of Contents

About This JDK Tutorial Book

Downloading and Installing JDK 1.8.0 on Windows

Downloading and Installing JDK 1.7.0 on Windows

Downloading and Installing JDK 1.6.2 on Windows

Java Date-Time API

Date, Time and Calendar Classes

Date and Time Object and String Conversion

Number Object and Numeric String Conversion

Locales, Localization Methods and Resource Bundles

Calling and Importing Classes Defined in Unnamed Packages