SocketIsConnected

bool  SocketIsConnected(
   const int  socket      // socket handle
   );

//+------------------------------------------------------------------+
//|                                            SocketIsConnected.mq5 |
//|                                  Copyright 2024, MetaQuotes Ltd. |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2024, MetaQuotes Ltd."
#property link      "https://www.mql5.com
#property version     "1.00"
#property description "Add Address to the list of allowed ones in the terminal settings to let the example work"
#property script_show_inputs
 
input string Address    ="www.mql5.com";
input int    Port       =80;
input bool   CloseSocket=true;
bool         ExtTLS     =false;
//+------------------------------------------------------------------+
//| Script program start function                                    |
//+------------------------------------------------------------------+
void OnStart(void)
  {
//--- create a socket and get its handle
   int socket=SocketCreate();
//--- check the handle
   if(socket!=INVALID_HANDLE)
     {
      //--- if all is well, connect
      if(SocketConnect(socket,Address,Port,1000))
        {
         PrintFormat("Established connection to %s:%d",Address,Port);
 
         string   subject,issuer,serial,thumbprint;
         datetime expiration;
         //--- if connection is protected by certificate, display its data
         if(SocketTlsCertificate(socket,subject,issuer,serial,thumbprint,expiration))
           {
            Print("TLS certificate:");
            Print("   Owner:      ",subject);
            Print("   Issuer:     ",issuer);
            Print("   Number:     ",serial);
            Print("   Print:      ",thumbprint);
            Print("   Expiration: ",expiration);
            ExtTLS=true;
           }
         //--- send GET request to the server
         if(HTTPSend(socket,"GET / HTTP/1.1\r\nHost: www.mql5.com\r\nUser-Agent: MT5\r\n\r\n"))
           {
            Print("GET request sent");
            //--- read response
            if(!HTTPRecv(socket,1000))
               Print("Failed to get a response, error ",GetLastError());
           }
         else
            Print("Failed to send GET request, error ",GetLastError());
        }
      else
        {
         PrintFormat("Connection to %s:%d failed, error %d",Address,Port,GetLastError());
        }
      //--- if the flag is set, close the socket after use
      if(CloseSocket)
         SocketClose(socket);
     }
   else
      Print("Failed to create a socket, error ",GetLastError());
 
//--- check server connection
   bool connected=SocketIsConnected(socket);
//--- terminate operation if no connection
   if(!connected)
     {
      Print("No connection to server");
     }
//--- if server connection is present
   else
     {
      Print("Connection to the server is available\nThe connection needs to be closed. Closing");
      //--- close the socket and check the connection status again
      SocketClose(socket);
      connected=SocketIsConnected(socket);
     }
 
//--- display the current server connection status
   Print("Currently connected: ",(connected ? "opened" : "closed"));
   /*
   result in case CloseSocket = true:
   No connection to server
   Currently connected: closed
 
   result in case CloseSocket = false:
   Connection to the server is available
   The connection needs to be closed. Closing
   Currently connected: closed
   */
  }
//+------------------------------------------------------------------+
//| Send command to server                                           |
//+------------------------------------------------------------------+
bool HTTPSend(int socket,string request)
  {
//--- convert the string to a character array, discard the terminating zero
   char req[];
   int  len=StringToCharArray(request,req)-1;
 
   if(len<0)
      return(false);
//--- if a secure TLS connection via port 443 is used
   if(ExtTLS)
      return(SocketTlsSend(socket,req,len)==len);
//--- if a regular TCP connection is used
   return(SocketSend(socket,req,len)==len);
  }
//+------------------------------------------------------------------+
//| Read server response                                             |
//+------------------------------------------------------------------+
bool HTTPRecv(int socket,uint timeout_ms)
  {
   char   rsp[];
   string result;
   ulong  timeout_check=GetTickCount64()+timeout_ms;
//--- read data from the socket while there is some, but not longer than timeout
   do
     {
      uint len=SocketIsReadable(socket);
 
      if(len)
        {
         int rsp_len;
         //--- different read commands depending on whether the connection is secure or not
         if(ExtTLS)
            rsp_len=SocketTlsRead(socket,rsp,len);
         else
            rsp_len=SocketRead(socket,rsp,len,timeout_ms);
         //--- parse response
         if(rsp_len>0)
           {
            result+=CharArrayToString(rsp,0,rsp_len);
            //--- display response header only
            int header_end=StringFind(result,"\r\n\r\n");
 
            if(header_end>0)
              {
               Print("HTTP answer header received:");
               Print(StringSubstr(result,0,header_end));
               return(true);
              }
            //--- update read timeout expiration time
            timeout_check=GetTickCount64()+timeout_ms;
           }
        }
     }
   while(GetTickCount64()<timeout_check && !IsStopped());
 
   return(false);
  }