Question: Autodotect SSL connection on same port

[RoLex]

Hello and thank you for this amazing set of cross platform sockets!

I'm currently working on an ancient TCP based protocol for chat between clients.

Server is running on single port, unlike HTTP vs HTTPS server.

When a client connects, the server speaks first to welcome new user.

Previosly this protocol did not have SSL support, but I would like to add it.

When a client connects using SSL, it talks first with SSL handshake request.

My idea is to wait a second to see if client is talking first, then start SSL handshake. Otherwise talk first to welcome non SSL user.

In Indy for example, this setting is called "bypass". With help of reading buffer in "peek" mode, it is possible to detect such clients.

So my question is simple: Is it possible to autodetect SSL connections on same port?

For example start server as non SSL, then on client connect peek the data, and manually call SSL hanshake if needed.

Thank you!

[RoLex]

--- Delphi-Cross-Socket-master/Net/Net.CrossSslSocket.Base.pas	Mon Apr 27 09:31:39 2026
+++ Delphi-Cross-Socket/Net/Net.CrossSslSocket.Base.pas	Thu Apr 30 12:11:16 2026
@@ -50,6 +50,7 @@
   ICrossSslSocket = interface(ICrossSocket)
   ['{A4765486-A0F1-4EFD-BC39-FA16AED21A6A}']
     function GetSsl: Boolean;
+    function GetWait: Integer;
     function GetSslMaxPendingWriteBytes: Int64;
     procedure SetSslMaxPendingWriteBytes(const AValue: Int64);
 
@@ -127,6 +128,7 @@
     ///   是否已启用 SSL
     /// </summary>
     property Ssl: Boolean read GetSsl;
+    property Wait: Integer read GetWait;
 
     /// <summary>
     ///   每条 SSL 连接 pending write 队列的明文字节上限.
@@ -155,13 +157,15 @@
   TCrossSslSocketBase = class(TCrossSocket, ICrossSslSocket)
   private
     FSsl: Boolean;
+    FWait: Integer;
     FSslMaxPendingWriteBytes: Int64;
   protected
     function GetSsl: Boolean;
+    function GetWait: Integer;
     function GetSslMaxPendingWriteBytes: Int64;
     procedure SetSslMaxPendingWriteBytes(const AValue: Int64);
   public
-    constructor Create(const AIoThreads: Integer; const ASsl: Boolean); reintroduce; virtual;
+    constructor Create(const AIoThreads: Integer; const ASsl: Boolean; const AWait: Integer = 0); reintroduce; virtual;
 
     procedure SetCertificate(const ACertBuf: Pointer; const ACertBufSize: Integer); overload; virtual; abstract;
     procedure SetCertificate(const ACertBytes: TBytes); overload; virtual;
@@ -174,6 +178,7 @@
     procedure SetPrivateKeyFile(const APKeyFile: string); virtual;
 
     property Ssl: Boolean read GetSsl;
+    property Wait: Integer read GetWait;
     property SslMaxPendingWriteBytes: Int64 read GetSslMaxPendingWriteBytes write SetSslMaxPendingWriteBytes;
   end;
 
@@ -182,11 +187,13 @@
 { TCrossSslSocketBase }
 
 constructor TCrossSslSocketBase.Create(const AIoThreads: Integer;
-  const ASsl: Boolean);
+  const ASsl: Boolean;
+  const AWait: Integer = 0);
 begin
   inherited Create(AIoThreads);
 
   FSsl := ASsl;
+  FWait := AWait;
   // pending write 队列默认上限 4 MB (大文件分片 + 防恶意 OOM 平衡)
   FSslMaxPendingWriteBytes := 4 * 1024 * 1024;
 end;
@@ -194,6 +201,11 @@
 function TCrossSslSocketBase.GetSsl: Boolean;
 begin
   Result := FSsl;
+end;
+
+function TCrossSslSocketBase.GetWait: Integer;
+begin
+  Result := FWait;
 end;
 
 function TCrossSslSocketBase.GetSslMaxPendingWriteBytes: Int64;

--- Delphi-Cross-Socket-master/Net/Net.CrossSslSocket.OpenSSL.pas	Mon Apr 27 09:31:39 2026
+++ Delphi-Cross-Socket/Net/Net.CrossSslSocket.OpenSSL.pas	Thu Apr 30 12:27:12 2026
@@ -52,6 +52,7 @@
       Callback: TCrossConnectionCallback;
     end;
   private
+    FSsl: Boolean;
     FSslData: PSSL;
     FBIOIn, FBIOOut: PBIO;
     FLock: ILock;
@@ -153,7 +154,7 @@
       const AConnectType: TConnectType; const AHost: string;
       const AConnectCb: TCrossConnectionCallback): ICrossConnection; override;
   public
-    constructor Create(const AIoThreads: Integer; const ASsl: Boolean); override;
+    constructor Create(const AIoThreads: Integer; const ASsl: Boolean; const AWait: Integer = 0); override;
     destructor Destroy; override;
 
     procedure SetCertificate(const ACertBuf: Pointer; const ACertBufSize: Integer); overload; override;
@@ -181,6 +182,7 @@
   const AHost: string; const AConnectedCb: TCrossConnectionCallback);
 begin
   inherited Create(AOwner, AClientSocket, AConnectType, AHost, AConnectedCb);
+  FSsl := Ssl;
 
   if Ssl then
   begin
@@ -205,7 +207,7 @@
 
 destructor TCrossOpenSslConnection.Destroy;
 begin
-  if Ssl then
+  if Ssl and FSsl then
   begin
     // pending writes 析构 drain: 把所有挂起 callback 以 fail 通知上层,
     // 上层闭包持有的 TBytes 才能释放 (零拷贝契约). 传 nil connection 避免
@@ -227,7 +229,7 @@
 procedure TCrossOpenSslConnection.DirectSend(const ABuffer: Pointer;
   const ACount: Integer; const ACallback: TCrossConnectionCallback);
 begin
-  if Ssl then
+  if Ssl and FSsl then
     _SslSend(ABuffer, ACount, ACallback)
   else
     _Send(ABuffer, ACount, ACallback);
@@ -235,7 +237,10 @@
 
 function TCrossOpenSslConnection.GetSslInfo(var ASslInfo: TSslInfo): Boolean;
 begin
-  Result := TSSLTools.GetSslInfo(FSslData, ASslInfo);
+  if FSsl then
+    Result := TSSLTools.GetSslInfo(FSslData, ASslInfo)
+  else
+    Result := False;
 end;
 
 procedure TCrossOpenSslConnection._Lock;
@@ -741,9 +746,9 @@
 
 { TCrossOpenSslSocket }
 
-constructor TCrossOpenSslSocket.Create(const AIoThreads: Integer; const ASsl: Boolean);
+constructor TCrossOpenSslSocket.Create(const AIoThreads: Integer; const ASsl: Boolean; const AWait: Integer = 0);
 begin
-  inherited Create(AIoThreads, ASsl);
+  inherited Create(AIoThreads, ASsl, AWait);
 
   if Ssl then
   begin
@@ -899,6 +904,19 @@
 
   if Ssl then
   begin
+    if (Wait > 0) and (TSocketAPI.Readable(LConnection.Socket, Wait) = 0) then begin
+      LConnection.FSsl := False;
+
+      if LConnection.FPendingWrites <> nil then
+        LConnection.FPendingWrites.Free;
+
+      if LConnection.FSslData <> nil then
+        SSL_free(LConnection.FSslData);
+
+      _Connected(LConnection);
+      Exit;
+    end;
+
     LHandshakeData := nil;
     LFatal := False;
 
@@ -945,6 +963,12 @@
   if Ssl then
   begin
     LConnectionObj := AConnection as TCrossOpenSslConnection;
+
+    if not LConnectionObj.FSsl then begin
+      _Received(AConnection, ABuf, ALen);
+      Exit;
+    end;
+
     LTriggerConnected := False;
     LDecryptedData := nil;
     LHandshakeData := nil;

Now it is possible, but only for my protocol where server talks first:

LServer := TCrossServer.Create(2, True, 500); // wait 500 ms

This could be extended to Recv() using MSG_PEEK and looking for first 2 bytes Byte(22) and Byte(03) which are part of SSL handshake.