Examples: MetaTrader 4 Expert Advisor exchanges information with the outside world - page 2

Han Hui Tan
1072
Han Hui Tan  
more:

Hi michaelt4268 !

The problem is  NetEventsProcDLL.dll functions are  designed to work with ANSI string but new MT4 works with UNICODE string.

For your separate example you should manage in such way:

For MT4 - correct:

1. 

#import "NetEventsProcDLL.dll"

// Only for Clients:

int ConnectTo(uchar&  ps8_ServerIP[], // in - string ps8_ServerIP = "0123456789123456"

              int     s32_Port,     // in 

              int&    ph_Client[]); // out - int ph_Client[1]

...

...

...

#import 

      

2. Before call to  ConnectTo(...)

   make conversion UNICODE string to ANSI string: 

    uchar uc_ServerIP[];

   StringToCharArray(ps8_ServerIP, uc_ServerIP);

   and now you can connect to server -  

    s32_Error = ConnectTo(uc_ServerIP, s32_Port, ph_Client);        

3.   NetEventsProcDLL.mgh

    correct this line -

   was -  string GetErrMsg(int ps32_Error)

   needed so -  string GetErrMsg(uint ps32_Error)

 

You example should work after that, but other examples should be corrected  this way too.

Besides include NetEventsProcDLL.dll functions defitnition c++ file must be corrected for another examples.

 

Regards

Sergey 

 



Dear Sergey,

 

Very much thanks. I successfully connect to the server after changing what you mentioned above.

And the metatrader4(client) also writes Double datatype successfully to echoserver as shown below.


However, the metatrader4(client) fails to read from the echoserver.

I check the ps32ReadLen[0] value which is 0 as shown below. If I understand correctly, no int elements have been read.

 

Pleas advise. dear experts here. 

[Deleted]  
michaelt4268:

Dear Sergey,

 

Very much thanks. I successfully connect to the server after changing what you mentioned above.

And the metatrader4(client) also writes Double datatype successfully to echoserver as shown below.


However, the metatrader4(client) fails to read from the echoserver.

I check the ps32ReadLen[0] value which is 0 as shown below. If I understand correctly, no int elements have been read.

 

Pleas advise. dear experts here. 

Hi amigo.

Please send me your MT4 client EA, something wrong in it, I'll look at.

Regards,

Sergey 

Han Hui Tan
1072
Han Hui Tan  
more:

Hi amigo.

Please send me your MT4 client EA, something wrong in it, I'll look at.

Regards,

Sergey 

//+---------------------------------------------------------------------------+
//|                                            Client.mq4                     |
//|                      Copyright © 2012, http://www.mql4.com/ru/users/more  |
//|                                       tradertobe@gmail.com                |
//+---------------------------------------------------------------------------+
#property copyright "Copyright © 2012, http://www.mql4.com/ru/users/more"
#property link      "http://www.mql4.com/ru/users/more"
#include <ImportNetEventsProcDLL.mqh>
/*int ConnectTo(string  ps8_ServerIP, // in - string ps8_ServerIP = "0123456789123456"
                int     s32_Port,     // in 
                int&    ph_Client[]); // out - int ph_Client[1]
*/
/*int SendToDouble(int     h_Client,        // in
                   double& pd_SendBuf[],    // in
                   int     s32_SendBufLen); // in - SendBuf[] array size in double element 
*/
/*int ReadFromDouble(int     h_Client,        // in
                     double& pd_ReadBuf[],    // in
                     int     s32_ReadBufLen,  // in  - ReadBuf[] array size in double element
                     int&    ps32_ReadLen[]); // out - int ps32_ReadLen[1] - count of actually read data in double element
*/                      
/*int ConnectClose(int h_Client);    // in
*/ 
       
// Globals variables
int s32_Error;
int i;
// for int ConnectTo(ps8_ServerIP, s32_Port, ph_Client);  // out - int h_Client[1]
string ps8_ServerIP = "192.168.1.2";  // mine local IP:192.168.1.7 
uchar  uc_ServerIP[];
int    s32_Port = 2000;  //default is 2000
int    ph_Client[1];

bool b_ConnectTo = false;

// for int SendToDouble(ph_Client[0], pd_Buf, s32_BufLen);  
// for int ReadFromDouble(ph_Client[0], pd_Buf, s32_BufLen, ps32_ReadLen);
double pd_Buf[1];
int    s32_BufLen = 1;
int    ps32_ReadLen[1];
//+------------------------------------------------------------------+
//| expert initialization function                                   |
//+------------------------------------------------------------------+
//+------------------------------------------------------------------+
//| expert deinitialization function                                 |
//+------------------------------------------------------------------+
void OnDeinit(const int reason)
{
//----
   if (b_ConnectTo)
   {
      s32_Error = ConnectClose(ph_Client[0]);
      Print("ConnectClose(...) return is: ",GetErrMsg(s32_Error));
      Alert("ConnectClose(...) return is: ",GetErrMsg(s32_Error));
      
      if (s32_Error == OK)
         b_ConnectTo = false;
   }
//----
   //return(0);
}  

void OnStart(){
//----

   //if (!b_ConnectTo)
     // return(0);

  StringToCharArray(ps8_ServerIP,uc_ServerIP);
   
   if(!b_ConnectTo)
   {
      s32_Error = ConnectTo(uc_ServerIP, s32_Port, ph_Client);
      Print("ConnectTo(...) return is: ",GetErrMsg(s32_Error));
      Alert("ConnectTo(...) return is: ",GetErrMsg(s32_Error));
      Print("ConnectTo(...) handle is: ",ph_Client[0]);
      Alert("ConnectTo(...) handle is: ",ph_Client[0]);
      
      if (s32_Error == OK)
      {
         b_ConnectTo = true;
         Print("Client now is ConnectTo the Server: ",ps8_ServerIP);
         Alert("Client now is ConnectTo the Server: ",ps8_ServerIP);
      }
   }
      
   RefreshRates();
   
   double pd_Value[1];
   
   pd_Value[0] = 1.8889; //NormalizeDouble(Bid,Digits);
      
   s32_Error = SendToDouble(ph_Client[0], pd_Value, s32_BufLen);
   
   
   if (s32_Error != 0)
   {
      Print("SendToDouble(",ph_Client[0],"...) return is: ",GetErrMsg(s32_Error));
      Alert("SendToDouble(",ph_Client[0],"...) return is: ",GetErrMsg(s32_Error));
     // return(1);
   }
   else
      Print("SendToDouble(",ph_Client[0],"...) return is: OK");
      Alert("SendToDouble(",ph_Client[0],"...) return is: OK");
      
   s32_Error = ReadFromDouble(ph_Client[0], pd_Buf, s32_BufLen, ps32_ReadLen);      
   
   if (s32_Error != 0)
   {
      Print("ReadFromDouble(",ph_Client[0],"...) return is: ", GetErrMsg(s32_Error));
      Alert("ReadFromDouble(",ph_Client[0],"...) return is: ", GetErrMsg(s32_Error));
      //return(1);
   }
   else
      Print("ReadFromDouble(",ph_Client[0],"...) return is: OK"); 
      Alert("ReadFromDouble(",ph_Client[0],"...) return is: OK"); 
   
   pd_Buf[0] = NormalizeDouble(pd_Buf[0],5);
   
   
   Print("ps32_ReadLen[0] value: ",IntegerToString(ps32_ReadLen[0]));
   Alert("ps32_ReadLen[0] value: ",IntegerToString(ps32_ReadLen[0]));
   
   if (ps32_ReadLen[0] > 0)
   {
      Print("Read double value is: ", pd_Buf[0]);
      Alert("Read double value is: ", pd_Buf[0]);
   }
      
   
//----
   //return(0);
  }
//+------------------------------------------------------------------+
// ImportNetEventsProcDLL.mqh

#import "NetEventsProcDLL.dll"
// Only for Clients:

int ConnectTo(uchar& ps8_ServerIP[], // in - string ps8_ServerIP = "0123456789123456"
              int     s32_Port,     // in 
              int&    ph_Client[]); // out - int ph_Client[1]
               
int ConnectClose(int h_Client);    // in
//
// Only for Server:
int ServerOpen(int  s32_Port);      // in

int GetAllConnections(int& ph_Client[],           // out - int ph_Client[62]
                      int& ps32_ClientIP[],       // out - int ps32_ClientIP[62]
                      int& ps32_ClientCount[]);   // out - int ps32_ClientCount[1]
                       
int DisconnectClient(int h_Client); // in

int ServerClose();
//
// For both: Clients and Server
int SendToInt   (int  h_Client,        // in
                 int& ps32_SendBuf[],  // in
                 int  s32_SendBufLen); // in - SendBuf[] array size in int element 
                 
int SendToDouble(int     h_Client,        // in
                 double& pd_SendBuf[],    // in
                 int     s32_SendBufLen); // in - SendBuf[] array size in double element 
                 
int SendToString(int    h_Client,        // in
                 uchar& ps8_SendBuf[],     // in
                 int    s32_SendBufLen); // in - SendBuf string size in char element              
                 

int ReadFromInt   (int h_Client,            // in
                   int& ps32_ReadBuf[],     // in 
                   int  s32_ReadBufLen,     // in  - ReadBuf[] array size in int element
                   int& ps32_ReadLen[]);    // out - int ps32_ReadLen[1] - count of actually read data in int element
                  
int ReadFromDouble(int     h_Client,        // in
                   double& pd_ReadBuf[],    // in
                   int     s32_ReadBufLen,  // in  - ReadBuf[] array size in double element
                   int&    ps32_ReadLen[]); // out - int ps32_ReadLen[1] - count of actually read data in double element
                   
int ReadFromString(int     h_Client,        // in
                   string  ps8_ReadBuf,     // in
                   int     s32_ReadBufLen,  // in  - ReadBuf   string size in char element
                   int&    ps32_ReadLen[]); // out - int ps32_ReadLen[1] - count of actually read data in char element
//                   
#import
//***************************************************************************************

#define WSAEINTR                 1004
#define WSAEBADF                 1009
#define WSAEACCES                10013
#define WSAEFAULT                10014
#define WSAEINVAL                10022
#define WSAEMFILE                10024
#define WSAEWOULDBLOCK           10035
#define WSAEINPROGRESS           10036
#define WSAEALREADY              10037
#define WSAENOTSOCK              10038
#define WSAEDESTADDRREQ          10039
#define WSAEMSGSIZE              10040
#define WSAEPROTOTYPE            10041
#define WSAENOPROTOOPT           10042
#define WSAEPROTONOSUPPORT       10043
#define WSAESOCKTNOSUPPORT       10044
#define WSAEOPNOTSUPP            10045
#define WSAEPFNOSUPPORT          10046
#define WSAEAFNOSUPPORT          10047
#define WSAEADDRINUSE            10048
#define WSAEADDRNOTAVAIL         10049 
#define WSAENETDOWN              10050 
#define WSAENETUNREACH           10051 
#define WSAENETRESET             10052 
#define WSAECONNABORTED          10053 
#define WSAECONNRESET            10054 
#define WSAENOBUFS               10055
#define WSAEISCONN               10056
#define WSAENOTCONN              10057
#define WSAESHUTDOWN             10058
#define WSAETOOMANYREFS          10059
#define WSAETIMEDOUT             10060
#define WSAECONNREFUSED          10061
#define WSAELOOP                 10062 
#define WSAENAMETOOLONG          10063
#define WSAEHOSTDOWN             10064 
#define WSAEHOSTUNREACH          10065
#define WSAENOTEMPTY             10066
#define WSAEPROCLIM              10067
#define WSAEUSERS                10068 
#define WSAEDQUOT                10069 
#define WSAESTALE                10070 
#define WSAEREMOTE               10071
#define WSASYSNOTREADY           10091
#define WSAVERNOTSUPPORTED       10092
#define WSANOTINITIALISED        10093
#define WSAEDISCON               10101
#define WSAENOMORE               10102
#define WSAECANCELLED            10103
#define WSAEINVALIDPROCTABLE     10104
#define WSAEINVALIDPROVIDER      10105
#define WSAEPROVIDERFAILEDINIT   10106
#define WSASYSCALLFAILURE        10107 
#define WSASERVICE_NOT_FOUND     10108
#define WSATYPE_NOT_FOUND        10109
#define WSA_E_NO_MORE            10110
#define WSA_E_CANCELLED          10111
#define WSAEREFUSED              10112
#define WSAHOST_NOT_FOUND        11001
#define WSATRY_AGAIN             11002 
#define WSANO_RECOVERY           11003
#define WSANO_DATA               11004
#define WSA_IO_PENDING           997 
#define WSA_IO_INCOMPLETE        996
#define WSA_INVALID_HANDLE       6 
#define WSA_INVALID_PARAMETER    87
#define WSA_NOT_ENOUGH_MEMORY    8
#define WSA_OPERATION_ABORTED    995

#define ERROR_INVALID_PARAMETER  88 //change to 88 due to conflict
#define INADDR_NONE              0xffffffff
#define ERROR_TIMEOUT            1460
#define OK                       0

// Get a human readable error message for an API error code
string GetErrMsg(uint s32_Errors)
{
        // Some translations of error codes are really stupid --> show the original error code.
        string s_NoExplanationYet = " - We have no yet explanation for this error";
        
        switch (s32_Errors)
        {
                case WSAEINTR:                return("WSAEINTR");  
                case WSAEBADF:                return("WSAEBADF"); 
                case WSAEACCES:               return("WSAEACCES");  
                case WSAEFAULT:               return("WSAEFAULT");  
                case WSAEINVAL:               return("WSAEINVAL");  
                case WSAEMFILE:               return("WSAEMFILE");  
                case WSAEWOULDBLOCK:          return("WSAEWOULDBLOCK");  
                case WSAEINPROGRESS:          return("WSAEINPROGRESS");  
                case WSAEALREADY:             return("WSAEALREADY");  
                case WSAENOTSOCK:             return("WSAENOTSOCK");  
                case WSAEDESTADDRREQ:         return("WSAEDESTADDRREQ");  
                case WSAEMSGSIZE:             return("WSAEMSGSIZE");  
                case WSAEPROTOTYPE:           return("WSAEPROTOTYPE");  
                case WSAENOPROTOOPT:          return("WSAENOPROTOOPT");  
                case WSAEPROTONOSUPPORT:      return("WSAEPROTONOSUPPORT");  
                case WSAESOCKTNOSUPPORT:      return("WSAESOCKTNOSUPPORT");  
                case WSAEOPNOTSUPP:           return("WSAEOPNOTSUPP");  
                case WSAEPFNOSUPPORT:         return("WSAEPFNOSUPPORT");  
                case WSAEAFNOSUPPORT:         return("WSAEAFNOSUPPORT");  
                case WSAEADDRINUSE:           return("WSAEADDRINUSE");  
                case WSAEADDRNOTAVAIL:        return("WSAEADDRNOTAVAIL");  
                case WSAENETDOWN:             return("WSAENETDOWN");  
                case WSAENETUNREACH:          return("WSAENETUNREACH");  
                case WSAENETRESET:            return("WSAENETRESET");  
                case WSAECONNABORTED:         return("WSAECONNABORTED");  
                case WSAECONNRESET:           return("WSAECONNRESET");  
                case WSAENOBUFS:              return("WSAENOBUFS");  
                case WSAEISCONN:              return("WSAEISCONN");  
                case WSAENOTCONN:             return("WSAENOTCONN");  
                case WSAESHUTDOWN:            return("WSAESHUTDOWN");  
                case WSAETOOMANYREFS:         return("WSAETOOMANYREFS");  
                case WSAETIMEDOUT:            return("WSAETIMEDOUT");  
                case WSAECONNREFUSED:         return("WSAECONNREFUSED");  
                case WSAELOOP:                return("WSAELOOP");  
                case WSAENAMETOOLONG:         return("WSAENAMETOOLONG");  
                case WSAEHOSTDOWN:            return("WSAEHOSTDOWN");  
                case WSAEHOSTUNREACH:         return("WSAEHOSTUNREACH");  
                case WSAENOTEMPTY:            return("WSAENOTEMPTY");  
                case WSAEPROCLIM:             return("WSAEPROCLIM");  
                case WSAEUSERS:               return("WSAEUSERS");  
                case WSAEDQUOT:               return("WSAEDQUOT");  
                case WSAESTALE:               return("WSAESTALE");  
                case WSAEREMOTE:              return("WSAEREMOTE");  
                case WSASYSNOTREADY:          return("WSASYSNOTREADY");  
                case WSAVERNOTSUPPORTED:      return("WSAVERNOTSUPPORTED");  
                case WSANOTINITIALISED:       return("WSANOTINITIALISED");  
                case WSAEDISCON:              return("WSAEDISCON");  
                case WSAENOMORE:              return("WSAENOMORE");  
                case WSAECANCELLED:           return("WSAECANCELLED");  
                case WSAEINVALIDPROCTABLE:    return("WSAEINVALIDPROCTABLE");  
                case WSAEINVALIDPROVIDER:     return("WSAEINVALIDPROVIDER");  
                case WSAEPROVIDERFAILEDINIT:  return("WSAEPROVIDERFAILEDINIT");  
                case WSASYSCALLFAILURE:       return("WSASYSCALLFAILURE");  
                case WSASERVICE_NOT_FOUND:    return("WSASERVICE_NOT_FOUND");  
                case WSATYPE_NOT_FOUND:       return("WSATYPE_NOT_FOUND");  
                case WSA_E_NO_MORE:           return("WSA_E_NO_MORE");  
                case WSA_E_CANCELLED:         return("WSA_E_CANCELLED");  
                case WSAEREFUSED:             return("WSAEREFUSED");  
                case WSAHOST_NOT_FOUND:       return("WSAHOST_NOT_FOUND");  
                case WSATRY_AGAIN:            return("WSATRY_AGAIN");  
                case WSANO_RECOVERY:          return("WSANO_RECOVERY");  
                case WSANO_DATA:              return("WSANO_DATA");  
                case WSA_IO_PENDING:          return("WSA_IO_PENDING");  
                case WSA_IO_INCOMPLETE:       return("WSA_IO_INCOMPLETE");  
                case WSA_INVALID_HANDLE:      return("WSA_INVALID_HANDLE");  
                case WSA_INVALID_PARAMETER:   return("WSA_INVALID_PARAMETER");  
                case WSA_NOT_ENOUGH_MEMORY:   return("WSA_NOT_ENOUGH_MEMORY");  
                case WSA_OPERATION_ABORTED:   return("WSA_OPERATION_ABORTED");  
                case ERROR_INVALID_PARAMETER: return("ERROR_INVALID_PARAMETER");
                case INADDR_NONE:             return("INADDR_NONE"); 
                case ERROR_TIMEOUT:           return("ERROR_TIMEOUT");
                case OK:                      return("OK");
                default:
                   return (DoubleToStr(s32_Errors,0)+s_NoExplanationYet);
        }
}

// Convert DWORD IP to string IP
string FormatIP(int IP)
{
   int s32_Byte0 = 0x000000FF & IP;
   int s32_Byte1 = 0x000000FF & (IP>>8);
   int s32_Byte2 = 0x000000FF & (IP>>16);
   int s32_Byte3 = 0x000000FF & (IP>>24);
   
   return(DoubleToStr(s32_Byte0,0)+"."+
          DoubleToStr(s32_Byte1,0)+"."+
          DoubleToStr(s32_Byte2,0)+"."+
          DoubleToStr(s32_Byte3,0));
}       

Dear Sergey,

 Above is the source code for the client.mq4 and ImportNetEventsProcDLL.mqh that I am using.

Thanks a lot.

Files:
[Deleted]  
michaelt4268:

Dear Sergey,

 Above is the source code for the client.mq4 and ImportNetEventsProcDLL.mqh that I am using.

Thanks a lot.

Hi amigo.

Here is EA that works as client, I tested  - it sends  and recieves.

Because now we have no any ticks(market is closed) I introduced Timer to call OnTick() function.

Please test and give me feedback.

 Regards,

Sergey

Files:
Client_1.mq4 5 kb
Han Hui Tan
1072
Han Hui Tan  
more:

Hi amigo.

Here is EA that works as client, I tested  - it sends  and recieves.

Because now we have no any ticks(market is closed) I introduced Timer to call OnTick() function.

Please test and give me feedback.

 Regards,

Sergey

Dear Sergey,

Yes, it is working now. Thanks friend. You are awesome.

Han Hui Tan
1072
Han Hui Tan  
more:

Hi amigo.

Here is EA that works as client, I tested  - it sends  and recieves.

Because now we have no any ticks(market is closed) I introduced Timer to call OnTick() function.

Please test and give me feedback.

 Regards,

Sergey

Dear Sergey,

 

After tried your demo working. I am shifting my work to communicate between your metatrader4 (client) code with my custom C++ application (server). 

 My C++ application (server) is written in QT and the network module used is QT QTCPSocket and QTCPServer. (*fyi not your library) 

The data transfer is successful from the metatrader 4 using your code to my C++ application.

However, the data transfer is not successful from my C++ application to the metatrader 4.

The metatrader4  code seems to not receive any data because  the variable ps32_ReadLen display 0 while communicating with my C++ application.

 

Some of my observation:

At the metatrader 4 client execution, the ReadFromDouble return code is 0, and the ps32ReadLen[0] value is 0 as well. According to your material above, it means there is no data in the client stack with specified handle.

However,I have double checked my C++ TCP server whereby, another TCP client can receive the data. 

 Some of my test:

I test my C++ TCP server using a 3rd party software SocketTest v 3.0.0

When the SocketTest(client) send "HelloServer", the server will resend back "888999000" as shown above. So i assume the TCP server has no problem sending out messages.

 

 

I use the 3rd party software to simulate as TCP server and tries to send messages to the metatrader4 client.

But  the variable ps32_ReadLen[0] value displays 0. This variable does display 1 when use your server.

 

The question I would like to ask is whether your metatrader 4 code can work with other C++ application.

If can, do you have any idea or any advise to me to solve the problem above? 

 

Thanks. 

[Deleted]  
michaelt4268:

Dear Sergey,

 

After tried your demo working. I am shifting my work to communicate between your metatrader4 (client) code with my custom C++ application (server). 

 My C++ application (server) is written in QT and the network module used is QT QTCPSocket and QTCPServer. (*fyi not your library) 

The data transfer is successful from the metatrader 4 using your code to my C++ application.

However, the data transfer is not successful from my C++ application to the metatrader 4.

The metatrader4  code seems to not receive any data because  the variable ps32_ReadLen display 0 while communicating with my C++ application.

 Metatrader 4 ReadFromDouble Code: 

Some of my observation:

At the metatrader 4 client execution, the ReadFromDouble return code is 0, and the ps32ReadLen[0] value is 0 as well. According to your material above, it means there is no data in the client stack with specified handle.

However,I have double checked my C++ TCP server whereby, another TCP client can receive the data. 

 

 The question I would like to ask is whether your metatrader 4 code can work with other C++ application.

If can, do you have any idea or any advise to me to solve the problem above? 

 

Thanks. 

DLL (Dynamic Link Library)  functions is universal mean to exchange  info between  any programs independantly on lang in which they were developed.

One only thing is important - every lang has it's own rules to call DLL fuctions, that's all.

So if you use mine DLL interface you have no any problems.

Han Hui Tan
1072
Han Hui Tan  
more:

DLL (Dynamic Link Library)  functions is universal mean to exchange  info between  any programs independantly on lang in which they were developed.

One only thing is important - every lang has it's own rules to call DLL fuctions, that's all.

So if you use mine DLL interface you have no any problems.

I didnt use your DLL on C++ Server application.

I use your mqh in the metatrader 4 client . 

Can it work this way? 

[Deleted]  
michaelt4268:

I didnt use your DLL on C++ Server application.

I use your mqh in the metatrader 4 client . 

Can it work this way? 

Yes it can, but MT4 client must know your  c++ server protocol, besides look at how MT4 DLL functions must be dtfined:

#import "NetEventsProcDLL.dll"
// Only for Clients:
int ConnectTo(uchar&  ps8_ServerIP[], // in - string ps8_ServerIP = "0123456789123456"
              int     s32_Port,     // in 
              int&    ph_Client[]); // out - int ph_Client[1]
                 
int ConnectClose(int h_Client);    // in
//
// Only for Server:
int ServerOpen(int  s32_Port);      // in

int GetAllConnections(int& ph_Client[],           // out - int ph_Client[62]
                      int& ps32_ClientIP[],       // out - int ps32_ClientIP[62]
                      int& ps32_ClientCount[]);   // out - int ps32_ClientCount[1]
                       
int DisconnectClient(int h_Client); // in

int ServerClose();
//
// For both: Clients and Server
int SendToInt   (int  h_Client,        // in
                 int& ps32_SendBuf[],  // in
                 int  s32_SendBufLen); // in - SendBuf[] array size in int element 
                 
int SendToDouble(int     h_Client,        // in
                 double& pd_SendBuf[],    // in
                 int     s32_SendBufLen); // in - SendBuf[] array size in double element 
                 
int SendToString(int    h_Client,        // in
                 uchar& ps8_SendBuf[],   // in
                 int    s32_SendBufLen); // in - SendBuf string size in char element
                 

int ReadFromInt   (int h_Client,            // in
                   int& ps32_ReadBuf[],     // in 
                   int  s32_ReadBufLen,     // in  - ReadBuf[] array size in int element
                   int& ps32_ReadLen[]);    // out - int ps32_ReadLen[1] - count of actually read data in int element
                  
int ReadFromDouble(int     h_Client,        // in
                   double& pd_ReadBuf[],    // in
                   int     s32_ReadBufLen,  // in  - ReadBuf[] array size in double element
                   int&    ps32_ReadLen[]); // out - int ps32_ReadLen[1] - count of actually read data in double element
                   
int ReadFromString(int     h_Client,        // in
                   uchar&  ps8_ReadBuf[],   // in
                   int     s32_ReadBufLen,  // in  - ReadBuf   string size in char element
                   int&    ps32_ReadLen[]); // out - int ps32_ReadLen[1] - count of actually read data in char element
//                   
#import
//***************************************************************************************

 After connection is established your MT4 client should use this funtions for info exchange with your c++ server, something like that:

   uchar uca_ReadBuffer[1000];
   int   s32_ReadBufLen = 1000;
   int   s32a_ReadLen[1];
   uint  u32_Error;
   
   string msw_Buffer = "";

   u32_Error = ReadFromString(h_Client, uca_ReadBuffer, s32_ReadBufLen,s32a_ReadLen); 

   if (u32_Error  == OK && s32a_ReadLen[0] != 0)
   {
       msw_Buffer = CharArrayToString(uca_ReadBuffer,0,s32a_ReadLen[0]);
   }

 

   uchar uca_SendBuffer[];
   int   s32_SendBufLen;
   uint  u32_Error;
   string msw_Buffer = "Text to send";
   StringToCharArray(msw_Buffer,uca_SendBuffer);
   
   s32_SendBufLen = StringLen(msw_Buffer);
   
   u32_Error = SendToString(h_Client,uca_SendBuffer,s32_SendBufLen); 
 
   if (u32_Error != 0)
   {
     ....
   }
   
[Deleted]  
more:

Yes it can, but MT4 client must know your  c++ server protocol, besides look at how MT4 DLL functions must be dtfined:

 After connection is established your MT4 client should use this funtions for info exchange with your c++ server, something like that:

 

I tested this java client/server.

Results are:

1. MT4 client can connect to it

2. MT4 client can send info to it and he recieves this info

2. MT4 client does't recieve info from this java client/server - the reason is my software is designed to send/recieve data blocks with variable length,

data block length  is contained in the 4 bytes header, so MT4 client don't read it's data from stack until data length equal to number in 4 bytes header,

but in the case when java server send only character strings  this number is very very very large !

 

So I should redo some things in my sofware for you to use it, or you should form data length  four bytes header for every data block to send to MT4 terminal.

In other words MT4 client and it's software environment waits input data in format : DWORD, Data.    DWORD - is 4 bytes header that comtains number of data itself + 4.