Calling DLL functions synchronously using asynchronous server

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C#

DLL

sockets

Thanks in Advance.

I have developed one Asynchronous Socket Server in C# [Console Application]. Main functionality of this server is to communicate with Hardware. This socket server receives data from client and sends to specific device. For sending data to hardware, dll is used. 3 dll functions are imported.

[DllImport(m_strPath, CharSet = CharSet.Auto)]
        public static extern int Net_Init(uint dwIP, int nIPPort, uint dwIDCode, int nTimeOut);

        [DllImport(m_strPath, CharSet = CharSet.Auto)]
        public static extern int Net_SendPicture(int nCardID, int nWndNo, int nPosX, int nPosY, int nCx, int nCy, IntPtr pPictureFile, int nSpeed, int nEffect, int nStayTime, int nPictRef);

        [DllImport(m_strPath, CharSet = CharSet.Auto)]
        public static extern int Net_SendText(int nCardID, int nWndNo, IntPtr pText, int crColor, int nFontSize, int nSpeed, int nEffect, int nStayTime, int nAlignment);

         [DllImport(m_strPath, CharSet = CharSet.Auto)]
        public static extern int Net_Disconnect();

When I am receiving request I am sending data to specific device. As request are multiple,
data is getting sent to other device.


For example

Thread 1 Req-1 Received
Req-1-Init Method Called for IP 2
Req-1-Sending text
Thread 2 Req-2 Received
Req-2-Init Method Called for IP 2
Req-1-Sending Picture ---------- Picture is getting sent to second hardware
Req-2-sendding Text
Req-1-Disconnect
Req-2-sending Picture

Please let me know the good approach so using Asynchronous client I can send data to hardware.
using DLL.

What I have tried:

I googled about synchronous Server but asynchronous socket server is best.