I found that if I try to pass a message larger than 65904 bytes - the
send() fails.
For pure cosmetic reasons I chosen to limit a message by 8192 bytes at
once. What is the recommended message length?
Tony.
Tony <mts.spb.suxx@mail.ru> wrote:
I found that if I try to pass a message larger than 65904 bytes - the
send() fails.
Are you using a local (on the same node) or remote TCPIP stack? That
value (65904) sounds like the largest message pass that is allowed
accross a QNX network. (It may, also, be the largest Send() officially
allowed (documented to be allowed) in the local case, but that this
limit is not enforced.)
As to whether send() should fragment and reconstruct, I don’t know.
For pure cosmetic reasons I chosen to limit a message by 8192 bytes at
once. What is the recommended message length?
I don’t know. But, anything above the MTU of the underlieing network is
going to get fragmented anyway. So, picking a convenient buffer size,
and 8K is a nice one, will probably work out well.
-David
David Gibbs
QNX Training Services
dagibbs@qnx.com
On Wed, 31 Jan 2007 23:00:11 +0300, David Gibbs <dagibbs@qnx.com> wrote:
Are you using a local (on the same node) or remote TCPIP stack?
I read in the paper docs that if I try to send() a larger message than is
atomically-sendable over the underlying protocol - the EMSGSIZE is
reported.
It was the TCP, it was on the local node, the lo0 MTU is 32976.
How much the allowed message size will drop if the routing decision were
to send() it through the en1, for example?
How do I know in advance what is the maximum size?
Also, how big the buffer is it possible to create via the SO_SNDBUF option?
Tony.