Python调用传感器DLL中的SDK函数，该函数接受指针IP和端口并返回void*（void*配置文件传感器的句柄）

Question

我刚接触Python。我正试图通过它的DLL库连接到一个激光传感器。这个库中的SDK函数是用C++语言编译的。你知道吗

通过在python中使用ctypes，我的第一个尝试是调用EthernetScanner\u Connect函数。功能参数如下：

void* EthernetScanner_Connect(char *chIP, char *chPort, int iTimeOut)

根据c++中的函数描述，如果连接失败，它应该返回空指针，否则它应该将句柄返回给profile sensor，这将在其他函数中使用。你知道吗

我的python代码到现在为止：

from ctypes import *

lib=windll.LoadLibrary("c:\\EthernetScanner.dll")

if lib:
    print("the Library is loaded")

EthernetScanner_Connect = getattr(lib,"EthernetScanner_Connect")

EthernetScanner_Connect.restype = c_void_p
EthernetScanner_Connect.argtypes =[c_char_p,c_char_p,c_int]
x = EthernetScanner_Connect(b"193.164.200.1\0",b"32407\0",0)

print(x)

因为我还没有连接到传感器，所以我希望该函数为空，但它给出了以下信息：

the Library is loaded
45940800

Answer 1

我想先指出[Python 3.Docs]: ctypes - A foreign function library for Python。你知道吗

我将根据一些假设发布一个答案：

1. 您所说的传感器与[FoxControls]: acuity-ap820-users-manual.pdf中描述的相同。如果这不是真的，答案是无用的

2. 根据上面的文档，EthernetScanner\u GetConnectStatus可能的返回状态是（emphasis是我的）：

   Status is a unsigned integer used as a buffer to contain the status code when the function returns.
   The status codes are:

   • 0: Disconnected
   • 1: Disconnecting
   • 2: Connecting
   • 3: Connected

   
   

   基于上述情况，以及连接超时为0的事实，我假设（文档中没有任何内容支持它）它尝试以非阻塞模式连接：

   • EthernetScanner\u Connect立即返回（意味着在尝试连接之前-如果您愿意，它“调度”连接操作）一个非空指针。对于非阻塞（异步）IO示例，请选中[MS.Docs]: connect function
   • 应该使用EthernetScanner\u GetConnectStatus定期查询（上述）指针。这就是为什么指针非NULL是有意义的（当EthernetScanner\u Connect返回时，连接尝试结果还不知道）

下面是一段应该用来处理这个问题的代码（不用说这是盲编码，意思是我实际上没有测试它）。
根据2^nd假设，如果传递的超时大于0，EthernetScanner\u Connect应返回NULL。你知道吗

代码.py：

#!/usr/bin/env python3

import sys
import ctypes
import time


DLL_NAME = "c:\\EthernetScanner.dll"

CONNECT_STATUS_DISCONNECTED = 0
CONNECT_STATUS_DISCONNECTING = 1
CONNECT_STATUS_CONNECTING = 2
CONNECT_STATUS_CONNECTED = 3

CONNECT_STATUSES_PENDING = [
    CONNECT_STATUS_CONNECTING,
    CONNECT_STATUS_DISCONNECTING,
]

def main():

    connect_timeout_msec = 0
    nb_mode = connect_timeout_msec == 0

    dll = ctypes.WinDLL(DLL_NAME)

    EthernetScanner_Connect = dll.EthernetScanner_Connect
    EthernetScanner_Connect.argtypes = [ctypes.c_char_p, ctypes.c_char_p, ctypes.c_uint32]
    EthernetScanner_Connect.restype = ctypes.c_void_p

    EthernetScanner_GetConnectStatus = dll.EthernetScanner_GetConnectStatus
    EthernetScanner_GetConnectStatus.argtypes = [ctypes.c_void_p, ctypes.POINTER(ctypes.c_uint32)]

    EthernetScanner_Disconnect = dll.EthernetScanner_Disconnect
    EthernetScanner_Disconnect.argtypes = [ctypes.c_void_p]
    EthernetScanner_Disconnect.restype = ctypes.c_uint32

    ptr = EthernetScanner_Connect(b"192.168.100.1", b"32001", connect_timeout_msec)
    if nb_mode:
        print("Non blocking mode: EthernetScanner_Connect returned {:}".format(ptr))
        poll_timeout_sec = 0.5
        connect_status = ctypes.c_int(CONNECT_STATUS_CONNECTING)
        while connect_status.value in CONNECT_STATUSES_PENDING:
            time.sleep(poll_timeout_sec)
            EthernetScanner_GetConnectStatus(ptr, ctypes.byref(connect_status))
        if connect_status.value != CONNECT_STATUS_CONNECTED:
            print("Couldn't connect (status: {:})!".format(connect_status.value))
            return
    else:
        print("Blocking mode: EthernetScanner_Connect returned {:}".format(ptr))
        if not ptr:
            print("Couldn't connect!")
            return

    # Do something with the sensor (pointer)

    EthernetScanner_Disconnect(ptr)


if __name__ == "__main__":
    print("Python {:s} on {:s}\n".format(sys.version, sys.platform))
    main()
    print("Done.")