解释

我目前正在尝试使用 python 脚本控制智能电源板。为了实现这一点，我使用了带有套接字模块的 TCP 连接。大约 75% 的情况下，我会得到我正在寻找的响应/数据，并且一切都运行良好。然而，大约 25% 的情况下，响应会以完全相同的长度（1024 字节）被截断。这对我来说没有任何意义，因为我的缓冲区大小实际上设置为 2048 字节。我在使用 recv() 之间等待的速度似乎也没有影响/导致这一点。尽管 TCP 是字节流，但这是否仍然可能与数据包碎片有关？

Code

主要代码

ip='192.168.0.62'
port=9999

sock_tcp = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
sock_tcp.connect((ip, port))
sock_tcp.send(encrypt('{"system":{"get_sysinfo":{}}}'))
data = sock_tcp.recv(2048)
sock_tcp.close()
print len(data) #On succesful runs output is 1221, on unsuccesful runs it is 1024
rec = decrypt(data[4:])
print str(rec) #See output below

加密功能

def encrypt(string):
    key = 171
    result = pack('>I', len(string))
    for i in string:
        a = key ^ ord(i)
        key = a
        result += chr(a)
    return result

解密功能

def decrypt(string):
    key = 171
    result = ""
    for i in string:
        a = key ^ ord(i)
        key = ord(i)
        result += chr(a)
    return result

Output

我收到的字符串本身。它很可能不相关，但我想无论如何我都会包含它。这是变量rec 的值。

所需的常规输出

完全所需的输出

{“system”：{“get_sysinfo”：{“sw_ver”：“1.0.6 内部版本 180627 Rel.081000","hw_ver":"1.0","型号":"HS300(美国)","deviceId":"80067B24A755F99C4D6C1807455E09F91AB7B2AA","oemId":"5C9E6254BEBAED63B2B6102966D24C17", “hwId”：“34C41AA028022D0CCEA5E678E8547C54”，“rssi ":-60,"longitude_i":-1222955,"latitude_i":379078,"alias":"TP-LINK_Power Strip_4F01","mic_type":"IOT.SMARTPLUGSWITCH","feature":"TIM:ENE","mac":"B0:BE:76:12:4F:01","更新":0,"led_off" :0,"children":[{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA00","state":0,"alias":"CezHeat","on_time":0,"next_action":{"type":-1}} ,{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA01","state":1,"alias":"CezUVB","on_time":191208,"next_action":{"type":-1}},{"id":" 80067B24A755F99C4D6C1807455E09F91AB7B2AA02","state":1,"alias":"CyanHeat","on_time":191208,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C18074 55E09F91AB7B2AA03","状态": 1、“别名”：“ZanderHeat”、“on_time”：191208、“next_action”：{“type”：-1}}、{“id”：“80067B24A755F99C4D6C1807455E09F91AB7B2AA04”、“state”：1、“alias”：“ CairoHeat","on_time":191208,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA05","state":1,"alias":"KodaMister","on_time": 191208,"next_action":{"type":-1}}],"child_num":6,"err_code":0}}}

异常且罕见的输出

切断输出

{“system”：{“get_sysinfo”：{“sw_ver”：“1.0.6 内部版本 180627 Rel.081000","hw_ver":"1.0","型号":"HS300(美国)","deviceId":"80067B24A755F99C4D6C1807455E09F91AB7B2AA","oemId":"5C9E6254BEBAED63B2B6102966D24C17", “hwId”：“34C41AA028022D0CCEA5E678E8547C54”，“rssi ":-59,"longitude_i":-1222955,"latitude_i":379078,"alias":"TP-LINK_Power Strip_4F01","mic_type":"IOT.SMARTPLUGSWITCH","feature":"TIM:ENE","mac":"B0:BE:76:12:4F:01","更新":0,"led_off" :0,"children":[{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA00","state":0,"alias":"CezHeat","on_time":0,"next_action":{"type":-1}} ,{"id":"80067B24A755F99C4D6C1807455E09F91AB7B2AA01","state":1,"alias":"CezUVB","on_time":191207,"next_action":{"type":-1}},{"id":" 80067B24A755F99C4D6C1807455E09F91AB7B2AA02","state":1,"alias":"CyanHeat","on_time":191207,"next_action":{"type":-1}},{"id":"80067B24A755F99C4D6C18074 55E09F91AB7B2AA03","状态": 1、“别名”：“ZanderHeat”、“on_time”：191207、“next_action”：{“type”：-1}}、{“id”：“80067B24A755F99C4D6C1807455E09F91AB7B2AA04”、“state”：1、“alias”：“开罗热火","上

结论

如果有人能为我提供有关输出/流为何被切断的解决方案或解释，我将不胜感激。我使用了这个开源的很多代码module https://github.com/softScheck/tplink-smartplug/blob/master/tplink_smartplug.py。我也希望更多地了解这一切是如何运作的，所以如果你能解释更多一点，我将非常感激。

根据文档 https://docs.python.org/3/library/socket.html#socket.socket.recv， bufsize 参数仅指定要读取的最大数据量：

socket.recv(bufsize[ 标志]) 从套接字接收数据。回报 value 是表示接收到的数据的字节对象。最大值 一次接收的数据量由 bufsize 指定。请参阅 Unix 手册页 recv(2) 了解可选参数的含义 旗帜；它默认为零。

为了确保完整的数据传输，可以使用这样的函数，它等待套接字连接的结束（由recv返回的空字符串表示）：

def recv_all(connection):
    """
    Function for all data

    :param connection: socket connection
    :return: received data
    """
    data = list()
    while True:
        data.append(connection.recv(2048))
        if not data[-1]:
            return b''.join(data)

另一个可能更适合您的应用程序的示例可能是等待固定的消息大小（如您的问题所示为 1221）：

def recv_message(connection):
    data = list()
    transferred_bytes= 0
    while transferred_bytes < 1221:
        data.append(connection.recv(min(1221-transferred_bytes, 2048)))
        if not data[-1]:
            raise RuntimeError("socket connection broken")
        transferred_bytes += len(data[-1])
    return b''.join(data)