As has already been stated, use of the <> operator is a buffered operation. In the provided loop, you invoke the operator once. If there are 3 newlines within the received data, your program would have received up to the first, but the remaining data could well have been read off the socket by the buffering logic. The select would hang, because the socket is empty, but there is data in the buffer that you have not read.

I don't think that you have a choice about using non-blocking sockets. If you are receiving variable-length data, I can't recall a way to look at how much is in the socket buffer before reading. You can either read a char at a time, and keep checking via select (not very pretty), or switch to non-blocking.

You mention having switched to non-blocking mode. Did you do this using sysread/recv? Could we see the code that did not work in this instance?

In reply to Re: select appears to ignore pending data on socket. by Illuminatus
in thread select appears to ignore pending data on socket. by Zidane

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