Demultiplexing udp streams from different sources
0
My server is using a single udp socket to receive udp streams from different ip addresses. (All senders send to the same port).
When recv returns on the server with a chunk of data, might that chunk contain bytes from different sources?
Assuming not, is there a reliable way to determine which sender sent that entire chunk?
sockets udp
asked Nov 25 '18 at 12:22
David SacksteinDavid Sackstein
157111
add a comment |
0
My server is using a single udp socket to receive udp streams from different ip addresses. (All senders send to the same port).
When recv returns on the server with a chunk of data, might that chunk contain bytes from different sources?
Assuming not, is there a reliable way to determine which sender sent that entire chunk?
sockets udp
asked Nov 25 '18 at 12:22
David SacksteinDavid Sackstein
157111
add a comment |
0
0
0
My server is using a single udp socket to receive udp streams from different ip addresses. (All senders send to the same port).
When recv returns on the server with a chunk of data, might that chunk contain bytes from different sources?
Assuming not, is there a reliable way to determine which sender sent that entire chunk?
sockets udp
asked Nov 25 '18 at 12:22
David SacksteinDavid Sackstein
157111
My server is using a single udp socket to receive udp streams from different ip addresses. (All senders send to the same port).
When recv returns on the server with a chunk of data, might that chunk contain bytes from different sources?
Assuming not, is there a reliable way to determine which sender sent that entire chunk?
sockets udp
sockets udp
asked Nov 25 '18 at 12:22
David SacksteinDavid Sackstein
157111
asked Nov 25 '18 at 12:22
David SacksteinDavid Sackstein
157111
asked Nov 25 '18 at 12:22
David SacksteinDavid Sackstein
157111
asked Nov 25 '18 at 12:22
David SacksteinDavid Sackstein
157111
asked Nov 25 '18 at 12:22
David SacksteinDavid Sackstein
157111
157111
add a comment |
add a comment |
1 Answer
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In UDP, each chunk received will be exactly what a sender previously passed to ‘send()’ or ‘sendto()’ — unlike TCP, UDP maintains message boundaries.
You can find out the IP address and port the received packet was sent from by calling ‘recvfrom()’ instead of ‘recv()’. Those values will be written into the ‘struct inaddr_in’ that you provide a pointer to.
answered Nov 25 '18 at 16:53
Jeremy FriesnerJeremy Friesner
39.8k1080164
Hi Jeremy my question about demultiplexing was answered by Alex F. Your comment however is interesting. What happens if the message is larger than the MTU or larger than the internal socket buffer at the receiver? Surely then the data read by recvfrom will not be a complete message? Are you saying that a read by recvfrom will never contain data from more than one packet but that it is possible that a message may be split into more than one recvfrom call? Can you point to the documentation on this?
– David Sackstein
Nov 25 '18 at 17:25
I will ask this as a separate question
– David Sackstein
Nov 25 '18 at 20:58
1
If the data passed to send() is greater than the MTU, the packet will be transparently fragmented by the sender, and (if all fragments make it to the receiving machine) transparently re-assembled by the receiver before it is passed to you. (If any of the fragments don’t make it, they will all be silently dropped)
– Jeremy Friesner
Nov 26 '18 at 2:46
For UDP, the data passed to send() will match the data later returned by recv().
– Jeremy Friesner
Nov 26 '18 at 2:47
1
Only (1) and (4) will be visible to your code; the others you listed will be handled transparently by the tcp stack (ie if there is a checksum mismatch the tcp stack will simply drop the udp packet rather than hand you corrupted data)
– Jeremy Friesner
Nov 26 '18 at 20:41
|
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1 Answer
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1 Answer
1
active
oldest
votes
active
oldest
votes
active
oldest
votes
1
In UDP, each chunk received will be exactly what a sender previously passed to ‘send()’ or ‘sendto()’ — unlike TCP, UDP maintains message boundaries.
You can find out the IP address and port the received packet was sent from by calling ‘recvfrom()’ instead of ‘recv()’. Those values will be written into the ‘struct inaddr_in’ that you provide a pointer to.
answered Nov 25 '18 at 16:53
Jeremy FriesnerJeremy Friesner
39.8k1080164
Hi Jeremy my question about demultiplexing was answered by Alex F. Your comment however is interesting. What happens if the message is larger than the MTU or larger than the internal socket buffer at the receiver? Surely then the data read by recvfrom will not be a complete message? Are you saying that a read by recvfrom will never contain data from more than one packet but that it is possible that a message may be split into more than one recvfrom call? Can you point to the documentation on this?
– David Sackstein
Nov 25 '18 at 17:25
I will ask this as a separate question
– David Sackstein
Nov 25 '18 at 20:58
1
If the data passed to send() is greater than the MTU, the packet will be transparently fragmented by the sender, and (if all fragments make it to the receiving machine) transparently re-assembled by the receiver before it is passed to you. (If any of the fragments don’t make it, they will all be silently dropped)
– Jeremy Friesner
Nov 26 '18 at 2:46
For UDP, the data passed to send() will match the data later returned by recv().
– Jeremy Friesner
Nov 26 '18 at 2:47
1
Only (1) and (4) will be visible to your code; the others you listed will be handled transparently by the tcp stack (ie if there is a checksum mismatch the tcp stack will simply drop the udp packet rather than hand you corrupted data)
– Jeremy Friesner
Nov 26 '18 at 20:41
|
show 1 more comment
1
In UDP, each chunk received will be exactly what a sender previously passed to ‘send()’ or ‘sendto()’ — unlike TCP, UDP maintains message boundaries.
You can find out the IP address and port the received packet was sent from by calling ‘recvfrom()’ instead of ‘recv()’. Those values will be written into the ‘struct inaddr_in’ that you provide a pointer to.
answered Nov 25 '18 at 16:53
Jeremy FriesnerJeremy Friesner
39.8k1080164
Hi Jeremy my question about demultiplexing was answered by Alex F. Your comment however is interesting. What happens if the message is larger than the MTU or larger than the internal socket buffer at the receiver? Surely then the data read by recvfrom will not be a complete message? Are you saying that a read by recvfrom will never contain data from more than one packet but that it is possible that a message may be split into more than one recvfrom call? Can you point to the documentation on this?
– David Sackstein
Nov 25 '18 at 17:25
I will ask this as a separate question
– David Sackstein
Nov 25 '18 at 20:58
1
If the data passed to send() is greater than the MTU, the packet will be transparently fragmented by the sender, and (if all fragments make it to the receiving machine) transparently re-assembled by the receiver before it is passed to you. (If any of the fragments don’t make it, they will all be silently dropped)
– Jeremy Friesner
Nov 26 '18 at 2:46
For UDP, the data passed to send() will match the data later returned by recv().
– Jeremy Friesner
Nov 26 '18 at 2:47
1
Only (1) and (4) will be visible to your code; the others you listed will be handled transparently by the tcp stack (ie if there is a checksum mismatch the tcp stack will simply drop the udp packet rather than hand you corrupted data)
– Jeremy Friesner
Nov 26 '18 at 20:41
|
show 1 more comment
1
1
1
In UDP, each chunk received will be exactly what a sender previously passed to ‘send()’ or ‘sendto()’ — unlike TCP, UDP maintains message boundaries.
You can find out the IP address and port the received packet was sent from by calling ‘recvfrom()’ instead of ‘recv()’. Those values will be written into the ‘struct inaddr_in’ that you provide a pointer to.
answered Nov 25 '18 at 16:53
Jeremy FriesnerJeremy Friesner
39.8k1080164
In UDP, each chunk received will be exactly what a sender previously passed to ‘send()’ or ‘sendto()’ — unlike TCP, UDP maintains message boundaries.
You can find out the IP address and port the received packet was sent from by calling ‘recvfrom()’ instead of ‘recv()’. Those values will be written into the ‘struct inaddr_in’ that you provide a pointer to.
answered Nov 25 '18 at 16:53
Jeremy FriesnerJeremy Friesner
39.8k1080164
answered Nov 25 '18 at 16:53
Jeremy FriesnerJeremy Friesner
39.8k1080164
answered Nov 25 '18 at 16:53
Jeremy FriesnerJeremy Friesner
39.8k1080164
answered Nov 25 '18 at 16:53
Jeremy FriesnerJeremy Friesner
39.8k1080164
39.8k1080164
Hi Jeremy my question about demultiplexing was answered by Alex F. Your comment however is interesting. What happens if the message is larger than the MTU or larger than the internal socket buffer at the receiver? Surely then the data read by recvfrom will not be a complete message? Are you saying that a read by recvfrom will never contain data from more than one packet but that it is possible that a message may be split into more than one recvfrom call? Can you point to the documentation on this?
– David Sackstein
Nov 25 '18 at 17:25
I will ask this as a separate question
– David Sackstein
Nov 25 '18 at 20:58
1
If the data passed to send() is greater than the MTU, the packet will be transparently fragmented by the sender, and (if all fragments make it to the receiving machine) transparently re-assembled by the receiver before it is passed to you. (If any of the fragments don’t make it, they will all be silently dropped)
– Jeremy Friesner
Nov 26 '18 at 2:46
For UDP, the data passed to send() will match the data later returned by recv().
– Jeremy Friesner
Nov 26 '18 at 2:47
1
Only (1) and (4) will be visible to your code; the others you listed will be handled transparently by the tcp stack (ie if there is a checksum mismatch the tcp stack will simply drop the udp packet rather than hand you corrupted data)
– Jeremy Friesner
Nov 26 '18 at 20:41
|
show 1 more comment
Hi Jeremy my question about demultiplexing was answered by Alex F. Your comment however is interesting. What happens if the message is larger than the MTU or larger than the internal socket buffer at the receiver? Surely then the data read by recvfrom will not be a complete message? Are you saying that a read by recvfrom will never contain data from more than one packet but that it is possible that a message may be split into more than one recvfrom call? Can you point to the documentation on this?
– David Sackstein
Nov 25 '18 at 17:25
I will ask this as a separate question
– David Sackstein
Nov 25 '18 at 20:58
1
If the data passed to send() is greater than the MTU, the packet will be transparently fragmented by the sender, and (if all fragments make it to the receiving machine) transparently re-assembled by the receiver before it is passed to you. (If any of the fragments don’t make it, they will all be silently dropped)
– Jeremy Friesner
Nov 26 '18 at 2:46
For UDP, the data passed to send() will match the data later returned by recv().
– Jeremy Friesner
Nov 26 '18 at 2:47
1
Only (1) and (4) will be visible to your code; the others you listed will be handled transparently by the tcp stack (ie if there is a checksum mismatch the tcp stack will simply drop the udp packet rather than hand you corrupted data)
– Jeremy Friesner
Nov 26 '18 at 20:41
Hi Jeremy my question about demultiplexing was answered by Alex F. Your comment however is interesting. What happens if the message is larger than the MTU or larger than the internal socket buffer at the receiver? Surely then the data read by recvfrom will not be a complete message? Are you saying that a read by recvfrom will never contain data from more than one packet but that it is possible that a message may be split into more than one recvfrom call? Can you point to the documentation on this?
– David Sackstein
Nov 25 '18 at 17:25
Hi Jeremy my question about demultiplexing was answered by Alex F. Your comment however is interesting. What happens if the message is larger than the MTU or larger than the internal socket buffer at the receiver? Surely then the data read by recvfrom will not be a complete message? Are you saying that a read by recvfrom will never contain data from more than one packet but that it is possible that a message may be split into more than one recvfrom call? Can you point to the documentation on this?
– David Sackstein
Nov 25 '18 at 17:25
I will ask this as a separate question
– David Sackstein
Nov 25 '18 at 20:58
I will ask this as a separate question
– David Sackstein
Nov 25 '18 at 20:58
1
1
If the data passed to send() is greater than the MTU, the packet will be transparently fragmented by the sender, and (if all fragments make it to the receiving machine) transparently re-assembled by the receiver before it is passed to you. (If any of the fragments don’t make it, they will all be silently dropped)
– Jeremy Friesner
Nov 26 '18 at 2:46
If the data passed to send() is greater than the MTU, the packet will be transparently fragmented by the sender, and (if all fragments make it to the receiving machine) transparently re-assembled by the receiver before it is passed to you. (If any of the fragments don’t make it, they will all be silently dropped)
– Jeremy Friesner
Nov 26 '18 at 2:46
For UDP, the data passed to send() will match the data later returned by recv().
– Jeremy Friesner
Nov 26 '18 at 2:47
For UDP, the data passed to send() will match the data later returned by recv().
– Jeremy Friesner
Nov 26 '18 at 2:47
1
1
Only (1) and (4) will be visible to your code; the others you listed will be handled transparently by the tcp stack (ie if there is a checksum mismatch the tcp stack will simply drop the udp packet rather than hand you corrupted data)
– Jeremy Friesner
Nov 26 '18 at 20:41
Only (1) and (4) will be visible to your code; the others you listed will be handled transparently by the tcp stack (ie if there is a checksum mismatch the tcp stack will simply drop the udp packet rather than hand you corrupted data)
– Jeremy Friesner
Nov 26 '18 at 20:41
|
show 1 more comment
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