Read time data from server fast without new connection by tcpclient

Hello everyone,

I would like to get the current time from a website, similar to the answer in

https://de.mathworks.com/matlabcentral/answers/477336-how-can-i-get-date-and-time-from-nist-server, where the following was described:

Nist_Time = tcpclient('time.nist.gov',13);
tcpdata = read(Nist_Time);

The read command works fine for the first time, but if I try

tcpdata = read(Nist_Time);

again, only

[]

is returned. I suspect that the connection to the server is gone after the first call, but I don't know how to maintain it.

I look forward to your feedback!

Answer 1

[Zinea]

Hi PeLa,

The connection to the server remains after the first read. This can be checked using 'Nist_Time.Status' which returns the value ‘open’.

The issue of the second read returning an empty array is probably due to the reason that the server protocol is designed in such a way that it does not send additional data after the first message. The server keeping the TCP connection open might be an implementation detail or a timeout feature.

Since the server sends data once per connection, the most straightforward approach is to establish a new connection with the server every time data is to be read.

Here is a code snippet where the function ‘fetchNewTime()’ is called for each read:

time1 = fetchNewTime(); 

Time now: 11:03:10

pause(5); 
time2 = fetchNewTime(); 

Time now: 11:03:16

function timeStr = fetchNewTime() 
Nist_Time = tcpclient('time.nist.gov', 13); 
pause(0.5); 
tcpdata = read(Nist_Time); 
if numel(tcpdata) >= 24 
    timeStr = char(tcpdata); 
    timeStr = timeStr(17:24); 
    disp(['Time now: ', timeStr]) 
else 
    disp('Not enough data received in the read attempt.') 
end 
end 

NOTE: Add a pause after the call to ‘tcpclient’ as there may be delay in fetching the data from the server.

Hope it helps!

[PeLa]

Thank you for your answer!