简单的SNTP python脚本

Question

我需要帮助完成以下脚本：

import socket
import struct
import sys
import time

NTP_SERVER = '0.uk.pool.ntp.org'
TIME1970 = 2208988800L

def sntp_client():
    client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    data = str.encode('\xlb' + 47 * '\0')
    client.sendto(data, (NTP_SERVER, 123))
    data, addr = client.recvfrom(1024)
    if data:
        print('Response received from:', addr)
    t = struct.unpack('!12I', data)[10]
    t -= TIME1970
    print('\tTime: %s' % time.ctime(t))

if __name__ == '__main__':
    sntp_client()

预期产出：

Response received from: ('80.82.244.120', 123)
      Time: Tue Sep 13 14:49:38 2016

问题是程序没有提供任何输出。它看起来像是在：

data, addr = client.recvfrom(1024)

我希望有人能帮我这个忙。

Answer 1

下面是第二版 of Python网络编程手册的工作脚本

import socket, struct, sys, time

NTP_SERVER = '0.uk.pool.ntp.org'
TIME1970 = 2208988800

def sntp_client():
    client = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    data = '\x1b' + 47 * '\0'
    client.sendto(data.encode('utf-8'), (NTP_SERVER, 123))
    data, address = client.recvfrom(1024)
    if data: print('Response received from:', address)
    t = struct.unpack('!12I', data)[10] - TIME1970
    print('\tTime = %s' % time.ctime(t))

if __name__ == '__main__':
    sntp_client()

Answer 2

应该指出，接受答案忽略了时间戳的分数部分，例如，见IETF RFC5905，第13页。一个代码片段，包括它可能看起来像

import socket
import struct
import datetime

NTP_SERVER = '0.uk.pool.ntp.org'
NTP_DELTA = 2208988800 # given as system epoch (e.g. 1970-1-1) minus NTP epoch (1900-1-1) in [s]

with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as client:
    data = '\x1b' + 47 * '\0'
    client.sendto(data.encode('utf-8'), (NTP_SERVER, 123))
    data, _ = client.recvfrom(256)
    tx_s, tx_f = struct.unpack('!12I', data)[10:12] # seconds and fractional seconds
    tx_timestamp = (tx_s + float(tx_f)/2**32) - NTP_DELTA
    
print(datetime.datetime.fromtimestamp(tx_timestamp, datetime.timezone.utc)) 
# e.g.
# 2019-12-18 13:02:14.029521+00:00 # Note: UTC used here for output!

还要记住，这只返回传输时间戳(tx；服务器发送数据包时的时间)。如果您寻找毫秒，往返延迟可能是显着的(例如，参见链接RFC5905的第29页)。

Sidenote：套接字文档建议在with上下文中打开套接字，以便在不再需要时正确关闭它。

Answer 3

编写的脚本没有任何问题，您需要寻找服务器可能没有响应您的另一个原因，例如防火墙设置。我自己的python脚本几乎完全相同：

    #!/bin/env python

    import socket
    import struct
    import sys
    import time

    TIME1970 = 2208988800L      # Thanks to F.Lundh

    pow2_31 = pow(2,31)
    pow2_32 = pow(2,32)
    pow2_16 = pow(2,16)

    if len(sys.argv) < 2:
        sys.stderr.write("Usage : " + sys.argv[0] + " <SNTP server>")
        exit(1)

    server = sys.argv[1]

    client = socket.socket( socket.AF_INET, socket.SOCK_DGRAM )
    data = '\x1b' + 47 * '\0'
    time_start = time.time()
    try:
        client.sendto( data, ( server, 123 ))
        client.settimeout(2)
    except:
        print "server <%s> not recognized" % (server)
        exit(2)
    try:
        data, address = client.recvfrom( 1024 )
    except socket.timeout:
        print "timed out"
        exit(3)

    if data:
        time_reply = (time.time() - time_start) * 1000
        print 'received %d bytes  from %s in %d ms :' % (len(data), address, time_reply)
        upacket = struct.unpack( '!48B', data )
        print upacket

用法：

$ ./sntp_client.py 0.uk.pool.ntp.org

received 48 bytes  from ('83.170.75.28', 123) in 154 ms :
(28, 3, 3, 236, 0, 0, 1, 171, 0, 0, 3, 0, 20, 139, 208, 232, 219, 177, 86, 148, 230, 192, 1, 15, 0, 0, 0, 0, 0, 0, 0, 0, 219, 177, 88, 27, 60, 214, 85, 212, 219, 177, 88, 27, 60, 238, 157, 39)