With a UDP (DGRAM) socket
if i read() n bytes and the packet size is m bytes > n bytes
do i loose the m-n bytes?
I tried and i think as a default the answre is yes
But is there an option I can set that prevents this?
Here pread(3): read from file - Linux man page I found
but it seems valid only for TCP sockets and not for UDP socketsA read() from a STREAMS file can read data in three different modes: byte-stream mode, message-nondiscard mode, and message-discard mode. The default shall be byte-stream mode. This can be changed using the I_SRDOPT ioctl() request, and can be tested with I_GRDOPT ioctl(). In byte-stream mode, read() shall retrieve data from the STREAM until as many bytes as were requested are transferred, or until there is no more data to be retrieved. Byte-stream mode ignores message boundaries.
In STREAMS message-nondiscard mode, read() shall retrieve data until as many bytes as were requested are transferred, or until a message boundary is reached. If read() does not retrieve all the data in a message, the remaining data shall be left on the STREAM, and can be retrieved by the next read() call. Message-discard mode also retrieves data until as many bytes as were requested are transferred, or a message boundary is reached. However, unread data remaining in a message after the read() returns shall be discarded, and shall not be available for a subsequent read(), getmsg(), or getpmsg() call.