title: Establishing socket connection through proxy
body: <p>I found the following useful program to download a certificate. But my problem is, that the host (with the certificate) is only accessible through our company proxy. 
  How can I teach this program to connect through our proxy?</p>
  
  <pre><code>/**
   * Originally posted at: (not available now)
   * http://blogs.sun.com/andreas/resource/InstallCert.java
   * Use:
   * java InstallCert hostname
   * Example:
   *% java InstallCert ecc.fedora.redhat.com
   */
  
  import javax.net.ssl.*;
  
  import java.io.*;
  import java.net.Socket;
  import java.security.KeyStore;
  import java.security.MessageDigest;
  import java.security.cert.CertificateException;
  import java.security.cert.X509Certificate;
  
  /**
   * Class used to add the server's certificate to the KeyStore with your trusted
   * certificates.
   */
  public class InstallCert {
  
      public static void main(String[] args) throws Exception {
          String host;
          int port;
          char[] passphrase;
          if ((args.length == 1) || (args.length == 2)) {
              String[] c = args[0].split(":");
              host = c[0];
              port = (c.length == 1) ? 443 : Integer.parseInt(c[1]);
              String p = (args.length == 1) ? "changeit" : args[1];
              passphrase = p.toCharArray();
          } else {
              System.out.println("Usage: java InstallCert [:port] [passphrase]");
              return;
          }
  
          File file = new File("jssecacerts");
          if (file.isFile() == false) {
              char SEP = File.separatorChar;
              File dir = new File(System.getProperty("java.home") + SEP + "lib"
                      + SEP + "security");
              file = new File(dir, "jssecacerts");
              if (file.isFile() == false) {
                  file = new File(dir, "cacerts");
              }
          }
          System.out.println("Loading KeyStore " + file + "...");
          InputStream in = new FileInputStream(file);
          KeyStore ks = KeyStore.getInstance(KeyStore.getDefaultType());
          ks.load(in, passphrase);
          in.close();
  
          SSLContext context = SSLContext.getInstance("TLS");
          TrustManagerFactory tmf = TrustManagerFactory
                  .getInstance(TrustManagerFactory.getDefaultAlgorithm());
          tmf.init(ks);
          X509TrustManager defaultTrustManager = (X509TrustManager) tmf
                  .getTrustManagers()[0];
          SavingTrustManager tm = new SavingTrustManager(defaultTrustManager);
          context.init(null, new TrustManager[] { tm }, null);
          SSLSocketFactory factory = context.getSocketFactory();
  
          System.out
                  .println("Opening connection to " + host + ":" + port + "...");
          SSLSocket socket = (SSLSocket) factory.createSocket(host, port);
          socket.setSoTimeout(10000);
          try {
              System.out.println("Starting SSL handshake...");
              socket.startHandshake();
              socket.close();
              System.out.println();
              System.out.println("No errors, certificate is already trusted");
          } catch (SSLException e) {
              System.out.println();
              e.printStackTrace(System.out);
          }
  
          X509Certificate[] chain = tm.chain;
          if (chain == null) {
              System.out.println("Could not obtain server certificate chain");
              return;
          }
  
          BufferedReader reader = new BufferedReader(new InputStreamReader(
                  System.in));
  
          System.out.println();
          System.out.println("Server sent " + chain.length + " certificate(s):");
          System.out.println();
          MessageDigest sha1 = MessageDigest.getInstance("SHA1");
          MessageDigest md5 = MessageDigest.getInstance("MD5");
          for (int i = 0; i &lt; chain.length; i++) {
              X509Certificate cert = chain[i];
              System.out.println(" " + (i + 1) + " Subject "
                      + cert.getSubjectDN());
              System.out.println("   Issuer  " + cert.getIssuerDN());
              sha1.update(cert.getEncoded());
              System.out.println("   sha1    " + toHexString(sha1.digest()));
              md5.update(cert.getEncoded());
              System.out.println("   md5     " + toHexString(md5.digest()));
              System.out.println();
          }
  
          System.out
                  .println("Enter certificate to add to trusted keystore or 'q' to quit: [1]");
          String line = reader.readLine().trim();
          int k;
          try {
              k = (line.length() == 0) ? 0 : Integer.parseInt(line) - 1;
          } catch (NumberFormatException e) {
              System.out.println("KeyStore not changed");
              return;
          }
  
          X509Certificate cert = chain[k];
          String alias = host + "-" + (k + 1);
          ks.setCertificateEntry(alias, cert);
  
          OutputStream out = new FileOutputStream("jssecacerts");
          ks.store(out, passphrase);
          out.close();
  
          System.out.println();
          System.out.println(cert);
          System.out.println();
          System.out
                  .println("Added certificate to keystore 'jssecacerts' using alias '"
                          + alias + "'");
      }
  
      private static final char[] HEXDIGITS = "0123456789abcdef".toCharArray();
  
      private static String toHexString(byte[] bytes) {
          StringBuilder sb = new StringBuilder(bytes.length * 3);
          for (int b : bytes) {
              b &amp;= 0xff;
              sb.append(HEXDIGITS[b &gt;&gt; 4]);
              sb.append(HEXDIGITS[b &amp; 15]);
              sb.append(' ');
          }
          return sb.toString();
      }
  
      private static class SavingTrustManager implements X509TrustManager {
  
          private final X509TrustManager tm;
          private X509Certificate[] chain;
  
          SavingTrustManager(X509TrustManager tm) {
              this.tm = tm;
          }
  
          public X509Certificate[] getAcceptedIssuers() {
              throw new UnsupportedOperationException();
          }
  
          public void checkClientTrusted(X509Certificate[] chain, String authType)
                  throws CertificateException {
              throw new UnsupportedOperationException();
          }
  
          public void checkServerTrusted(X509Certificate[] chain, String authType)
                  throws CertificateException {
              this.chain = chain;
              tm.checkServerTrusted(chain, authType);
          }
      }
  }
  </code></pre>
  
  <p>I already tried adding the following, but it doesn't help:</p>
  
  <pre><code>/* Proxy settings */
  System.setProperty("http.proxyHost", "proxy.abc.com");
  System.setProperty("http.proxyPort", "80");
  </code></pre>
  
  <p>nor does something like that do any good:</p>
  
  <pre><code>Socket proxy = new Socket("proxy.abc.com", 80);
  SSLSocket socket =  (SSLSocket) factory.createSocket(proxy, host, port, false);
  </code></pre>
  
  <p>I always get the following exception:</p>
  
  <pre><code>Exception in thread "main" java.net.ConnectException: Connection timed out: connect
      at java.net.PlainSocketImpl.socketConnect(Native Method)
      at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:333)
      at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:195)
      at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:182)
      at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
      at java.net.Socket.connect(Socket.java:529)
      at com.sun.net.ssl.internal.ssl.SSLSocketImpl.connect(SSLSocketImpl.java:550)
      at com.sun.net.ssl.internal.ssl.SSLSocketImpl.&lt;init&gt;(SSLSocketImpl.java:353)
      at com.sun.net.ssl.internal.ssl.SSLSocketFactoryImpl.createSocket(SSLSocketFactoryImpl.java:71)
      at InstallCert.main(InstallCert.java:72)
  </code></pre>
  
  <p>Accessing the remote host through a browser also only works with active proxy. That's why I thought that I also need the proxy for the InstallCert-program.</p>