From 1e81b3320ccbe0e808edb94b54ce8c105577e1bf Mon Sep 17 00:00:00 2001
From: smilexs4 <benedeklaci2002@gmail.com>
Date: Thu, 25 Jul 2024 22:41:52 +0300
Subject: [PATCH 1/2] Update ModbusTLS.h

Pass host to WiFiClientSecure->connect() without converting it to IPAddress in order to avoid TLS error in case the server certificate has a hostname in its CN subject field.
---
 src/ModbusTLS.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/src/ModbusTLS.h b/src/ModbusTLS.h
index 7f0fdf8..906c2d3 100644
--- a/src/ModbusTLS.h
+++ b/src/ModbusTLS.h
@@ -86,13 +86,13 @@ class ModbusTLS : public ModbusAPI<ModbusTCPTemplate<WiFiServerSecure, WiFiClien
     #endif
 #if defined(MODBUSIP_USE_DNS)
     bool connect(String host, uint16_t port, const char* client_cert = nullptr, const char* client_private_key = nullptr, const char* ca_cert = nullptr) {
-        return connect(resolver(host.c_str()), port, client_cert, client_private_key, ca_cert);
+        return connect(resolver(host.c_str()), port, client_cert, client_private_key, ca_cert, host.c_str());
     }
     bool connect(const char* host, uint16_t port, const char* client_cert = nullptr, const char* client_private_key = nullptr, const char* ca_cert = nullptr) {
-        return connect(resolver(host), port, client_cert, client_private_key, ca_cert);
+        return connect(resolver(host), port, client_cert, client_private_key, ca_cert, host);
     }
 #endif
-    bool connect(IPAddress ip, uint16_t port, const char* client_cert = nullptr, const char* client_private_key = nullptr, const char* ca_cert = nullptr) {
+    bool connect(IPAddress ip, uint16_t port, const char* client_cert = nullptr, const char* client_private_key = nullptr, const char* ca_cert = nullptr, const char* host = nullptr) {
         if (!ip)
             return false;
         if(getSlave(ip) >= 0)
@@ -113,7 +113,11 @@ class ModbusTLS : public ModbusAPI<ModbusTCPTemplate<WiFiServerSecure, WiFiClien
         }
         #endif
         //return tcpclient[p]->connect(ip, port);
-        if (!tcpclient[p]->connect(ip, port))
+        if (host)
+          if (!tcpclient[p]->connect(host, port))
+            return false;
+        else 
+          if (!tcpclient[p]->connect(ip, port))
             return false;
         return true;
     }

From 2a38ca1d8c3971ff1ab9c7f13db66dafe6f1a4ed Mon Sep 17 00:00:00 2001
From: smilexs4 <benedeklaci2002@gmail.com>
Date: Sat, 27 Jul 2024 16:58:29 +0300
Subject: [PATCH 2/2] Update ModbusTLS.h

---
 src/ModbusTLS.h | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/ModbusTLS.h b/src/ModbusTLS.h
index 906c2d3..bd4c616 100644
--- a/src/ModbusTLS.h
+++ b/src/ModbusTLS.h
@@ -113,12 +113,14 @@ class ModbusTLS : public ModbusAPI<ModbusTCPTemplate<WiFiServerSecure, WiFiClien
         }
         #endif
         //return tcpclient[p]->connect(ip, port);
-        if (host)
+        if (host) {
           if (!tcpclient[p]->connect(host, port))
             return false;
-        else 
+        }
+        else {
           if (!tcpclient[p]->connect(ip, port))
             return false;
+        }
         return true;
     }
 };