SocketClientInit是C++里面定义的方法，通过EntryPoint = "?SocketClientInit@@YAHHHPAD@Z"指出这个函数的真正入口处，方法是在运行指令中输入

dumpbin -exports +dll 路径：dumpbin -exports C:\Users\Administrator\Desktop\C++Dll\C++Dll\bin\Debug\NcPcCom.dll

[DllImport("NcPcCom.dll", EntryPoint = "?SocketClientInit@@YAHHHPAD@Z", CallingConvention = CallingConvention.Cdecl)]
        public static extern int SocketClientInit(int TimeOut, int TimeOutCnt, ref string Ver);
        public int socketClientInit(int TimeOut, int TimeOutCnt, ref string Ver)
        {
            return SocketClientInit(TimeOut, TimeOutCnt, ref Ver);
        }