Dart

Socket Convert Existing TCP Connection to SSL/TLS

Demonstrates the Chilkat Socket ConvertToSsl method. Dart

import 'package:chilkat/chilkat.dart';

void main() {
  // This example requires the Chilkat API to have been previously unlocked.
  // See Global Unlock Sample for sample code.

  final sock = CkSocket();

  // --------------------------------------------------------------------
  // This example uses the public TCP/TLS echo service at https://tcpbin.com/
  // --------------------------------------------------------------------

  // The echo server at tcpbin.com expects to receive TCP connections on port 4242, and TLS connections on port 4243.
  // We could simply connect to port 4243 using TLS like this.
  // However, further below, this example shows how to initially make a TCP connection, and then convert the connection to TLS.
  var useTls = true;
  final port = 4243;
  final maxWaitMs = 5000;
  try {
    sock.connect('tcpbin.com', port, useTls, maxWaitMs);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // OK, we have a TLS connection.
  // Note: The server chooses the TLS protocol version. 
  // We can see the version of the TLS connection that was established:
  print('TLS version: ${sock.tlsVersion}');

  sock.close(maxWaitMs);

  // ---------------------------------------------------------------------
  // Now we'll do the same, except first we connect to port 4243 using TCP,
  // and then convert the connection to TLS.
  // 
  // This may seem pointless, and it is for the case w/ this server.  However, there could be situations
  // where you're interacting with a server of some kind where there is a need to convert to/from TLS.
  // (This is common internal to many protocols, such as SMTP, IMAP, FTP, etc., and it is often called "explicit" SSL/TLS)

  // Connect again, except this time useTls is false, so we only have a simple TCP connection after this call.
  useTls = false;
  try {
    sock.connect('tcpbin.com', port, useTls, maxWaitMs);
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // Convert the existing TCP connection to TLS.
  // (The method name uses "SSL" because long ago, at the time of initial development, TLS 1.0 did not yet exist.)
  try {
    sock.convertToSsl();
  } on ChilkatException catch (e) {
    print(e.lastErrorText);
    return;
  }

  // OK, we now have a TLS connection.
  // Again, we can see the TLS version:
  print('TLS version: ${sock.tlsVersion}');

  sock.close(maxWaitMs);
}