(Objective-C) Socket Convert Existing TCP Connection to SSL/TLS

Demonstrates the Chilkat Socket ConvertToSsl method.

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#import <CkoSocket.h>

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

CkoSocket *sock = [[CkoSocket alloc] init];

// --------------------------------------------------------------------
// 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.
BOOL useTls = YES;
int port = 4243;
int maxWaitMs = 5000;
BOOL success = [sock Connect: @"tcpbin.com" port: [NSNumber numberWithInt: port] ssl: useTls maxWaitMs: [NSNumber numberWithInt: maxWaitMs]];
if (success == NO) {
    NSLog(@"%@",sock.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:
NSLog(@"%@%@",@"TLS version: ",sock.TlsVersion);

[sock Close: [NSNumber numberWithInt: 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 NO, so we only have a simple TCP connection after this call.
useTls = NO;
success = [sock Connect: @"tcpbin.com" port: [NSNumber numberWithInt: port] ssl: useTls maxWaitMs: [NSNumber numberWithInt: maxWaitMs]];
if (success == NO) {
    NSLog(@"%@",sock.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.)
success = [sock ConvertToSsl];
if (success == NO) {
    NSLog(@"%@",sock.LastErrorText);
    return;
}

// OK, we now have a TLS connection.
// Again, we can see the TLS version:
NSLog(@"%@%@",@"TLS version: ",sock.TlsVersion);

[sock Close: [NSNumber numberWithInt: maxWaitMs]];