thanks for replying. how many bytes is taken by object u also. how many total bytes including data plus u
how to calculate number of byte send in UDP
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i send data in udp call.
u = udp('127.0.0.1', 8000);
fopen(u);
x = (0:999) .* 8 * pi / 1000;
data = sin(x);
fwrite(u, data, 'float32');
how many byte is sent in this fwrite call.
how to calculate byte using this call
please explain
similarly
fread(u, datas, 'float32');
how many byte is received in this fread call.
how to calculate byte using this call
thanks
Answers (2)
Uladzimir
on 14 Aug 2015
fwrite(u, data, 'float32') Here are numel(data)*4 bytes.
fread(u, datas, 'float32') Here are datas*4 bytes
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Walter Roberson
on 14 Aug 2015
udp takes 2*32 bits = 8 bytes, plus the length of the data (which here would be 4 bytes). But udp packets have to be embedded in IP packets, which take 5*32 bits = 20 bytes before the UDP packet.
But IP packets have to be embedded in a physical transport layer such as ethernet which require a number of bytes around the IP packet. The structure of Wi-Fi 802.11 packets is not the same as for Ethernet; more at http://www.wildpackets.com/resources/compendium/wireless_lan/wlan_packets#wp1000999
![](https://www.mathworks.com/matlabcentral/images/broken_image.png)
You need to decide on a particular physical transmission standard, and you need to decide what you want to include in your count. Do you count the preamble (historically it was allowed for some of the bytes to go missing in transit)? The Frame Check Sequence (a lot of people forget but it really should be included)? The Interpacket Gap (arguable, since it is a mandatory gap in transmission rather than data being transmitted)
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