(C#) Accept TLS Connection with Client Authentication

Demonstrates how to accept a TLS connection requiring client authentication. This is the case where the TLS client sends a certificate. It is also known as "Two-Way SSL".

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

Chilkat.Socket listenSslSocket = new Chilkat.Socket();

// An SSL/TLS server needs a digital certificate.  This example loads it from a PFX file.
// Note: This is the server's certificate.

Chilkat.Cert cert = new Chilkat.Cert();
// The 1st argument is the file path, the 2nd arg is the 
// PFX file's password:
bool success = cert.LoadPfxFile("chilkat.pfx","test");
if (success != true) {
    Debug.WriteLine(cert.LastErrorText);
    return;
}

// To accept client client certificates in the TLS handshake,
// we must indicate a list of acceptable client certificate root CA DN's
// that are allowed.  (DN is an acronym for Distinguished Name.)
// Call AddSslAcceptableClientCaDn once for each acceptable CA DN.
// Here are a few examples so you can see the general format of a DN.
listenSslSocket.AddSslAcceptableClientCaDn("C=SE, O=AddTrust AB, OU=AddTrust External TTP Network, CN=AddTrust External CA Root");
listenSslSocket.AddSslAcceptableClientCaDn("O=Digital Signature Trust Co., CN=DST Root CA X3");

// Use the certificate:
success = listenSslSocket.InitSslServer(cert);
if (success != true) {
    Debug.WriteLine(listenSslSocket.LastErrorText);
    return;
}

// Bind and listen on a port:
int myPort = 8123;
// Allow for a max of 5 queued connect requests.
int backLog = 5;
success = listenSslSocket.BindAndListen(myPort,backLog);
if (success != true) {
    Debug.WriteLine(listenSslSocket.LastErrorText);
    return;
}

// If accepting an SSL/TLS connection, the SSL handshake is part of the connection
// establishment process. This involves a few back-and-forth messages between the 
// client and server to establish algorithms and a shared key to create the secure 
// channel. The sending and receiving of these messages are governed by the 
// MaxReadIdleMs and MaxSendIdleMs properties. If these properties are set to 0 
// (and this is the default unless changed by your application), then the 
// AcceptNextConnection can hang indefinitely during the SSL handshake process. 
// Make sure these properties are set to appropriate values before calling AcceptNextConnection.

// Set a 10 second max for waiting to read/write.  This is for the SSL/TLS handshake establishment.
listenSslSocket.MaxReadIdleMs = 10000;
listenSslSocket.MaxSendIdleMs = 10000;

// Accept a single client connection and establish the secure SSL/TLS channel:
Chilkat.Socket clientSock = null;
int maxWaitMillisec = 20000;
clientSock = listenSslSocket.AcceptNextConnection(maxWaitMillisec);
if (listenSslSocket.LastMethodSuccess == false) {
    Debug.WriteLine(listenSslSocket.LastErrorText);
    return;
}

// The client (in this example) is going to send a "Hello Server! -EOM-" 
// message.  Read it:
string receivedMsg = clientSock.ReceiveUntilMatch("-EOM-");
if (clientSock.LastMethodSuccess != true) {
    Debug.WriteLine(clientSock.LastErrorText);
    return;
}

Debug.WriteLine(receivedMsg);

// Send a "Hello Client! -EOM-" message:
success = clientSock.SendString("Hello Client! -EOM-");
if (success != true) {
    Debug.WriteLine(clientSock.LastErrorText);
    return;
}

// Close the connection with the client
// Wait a max of 20 seconds (20000 millsec)
success = clientSock.Close(20000);