CODEWITHSUNDEEP
c++udp
herzl shemuelian
herzl shemuelian

Reputation: 3508

how to check used udp buffer status?

I have a program that recevice message in udp in visual studio.

sometime I miss a message.I want to use select to see udp buffer used size if udp rec buffer is full.

How I can use select for this purpose?

where can I see a example?

Upvotes: 2

Views: 2147

Answers (3)

Nikolai Fetissov
Nikolai Fetissov

Reputation: 84169

Post-fact discovery that your receive buffer is full will not do you any good - packets have already been dropped. Even more - you need to set your buffer sizes before connect() or bind(), they will not change after that.

What you should do is pre-set socket receive buffer to some large value that would accommodate your traffic spikes, and try to process your network input faster. That usually means doing select() on non-blocking sockets (or even better - some advanced API like Linux epoll(7) in edge-triggered mode), and draining socket input until you get EWOULDBLOCK.

Edit 0:

You cannot discover that you missed a UDP packet by using select() or any other socket API. This has to be done in the application-level protocol, i.e. one layer up from the transport. Common practice is including sequence numbers in application message header.

Upvotes: 4

Some programmer dude
Some programmer dude

Reputation: 409196

You can use getsockopt to get socket options, including receive buffer size. Use setsockopt to set the size.

Example of getting the size:

int size;
getsockopt(socket_fd, SOL_SOCKET, SO_RCVBUF, &size);
std::cout << "Buffer size is currently " << size << " bytes\n";

Upvotes: 3

David Grayson
David Grayson

Reputation: 87416

I think one of the main properties of UDP (as opposed to TCP) is that you will sometimes lose messages. You have to design your protocol to account for that. I'm not an expert in UDP, but I don't understand how seeing the size of the buffer will help you, and I don't understand why you want to use select to do it.

Upvotes: 2

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