Hello, reversecode, you wrote: R> initially my thought was another R> if UDP that is used for what sending of the packaged flow R> that R> 1) catching of packets recvfrom from different flows and in the general queue (the flow that is sent one) - in any way does not accelerate R> 2) the buffer for catching can be less than the biggest piece of the sent packet, R> and then we catch a smaller piece, we quit with recvfrom And? Other flow we catch the rest? We cannot catch smaller or the most part... We select the next datagram from the come. If it does not get into the buffer that we lose the datagram completely. No Axis will select that from entering datagrams that gets in transferred recvfrom the buffer. R> you contracted into the same subject where, we admit the maximum size which we catch in 65536 byte, almost 65 R> mbuf if I am not mistaken 4096 bytes, 4 kilobytes Yes this does not concern mbuf the buffer storing entering datagrams of a socket. . R> the come datagram in 65536 byte, R> and casually not sufficed places in the buffer (began clusters on 4 and did not suffice, well differently happens in OS) R> will be wetted hardly already on the accepted side (only I assume) R> variants two, 1) presoaks giving to the user an error (artful OS) R> 2) not to wet and give to the user so much how many came (friendly OS) R> to climb to look at least in about that as generally behave in such situations of OS, do not want And costs Because you described variants of mythical behavior which is not present in POSIX-sockets. At least I about such behavior never heard. Any option which forces sockets so to work, but by default they can and is I work on another. If the datagram is not accepted completely on the client (i.e. it is not put in the entering buffer of a socket), recvfrom locks program execution (if it did not translate in a non-blocking mode). Also will not be the first second variant. The first - the client does not receive an error that any datagram did not get into the buffer of a socket from an entering network. The second - because so UDP-sockets do not work.