簡單的 SNTP python 腳本

Question

我需要幫助來完成以下腳本：

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()

預期輸出：

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

問題是程序沒有給出任何輸出。 看起來它卡在：

data, addr = client.recvfrom(1024)

我希望有人能幫我解決這個問題。

Answer 1

這是Python Network Programming Cookbook第二版中的工作腳本：

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

應該注意的是，接受的答案忽略了時間戳的小數部分，例如參見IETF RFC5905 ，p.13。 包含它的代碼片段可能看起來像

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!

還要記住，這僅返回傳輸時間戳（tx；服務器發送數據包的時間）。 如果您尋找毫秒，則往返延遲可能很重要（請參閱鏈接的 RFC5905 的 egp29）。

旁注：套接字文檔建議在with上下文中打開套接字，以便在不再需要時正確關閉它。

Answer 3

您編寫的腳本沒有任何問題，您需要尋找服務器可能不響應您的另一個原因，例如防火牆設置。 我自己的python SNTP腳本幾乎完全一樣：

    #!/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)