Receives a message on a socket. Attempts to receive LENGTH characters of data into variable SCALAR from the specified SOCKET filehandle. SCALAR will be grown or shrunk to the length actually read. Takes the same flags as the system call of the same name. Returns the address of the sender if SOCKET's protocol supports this; returns an empty string otherwise. If there's an error, returns the undefined value. This call is actually implemented in terms of recvfrom(2) system call. See perlipc/"UDP: Message Passing" for examples.
Note the characters: depending on the status of the socket, either
(8-bit) bytes or characters are received. By default all sockets
operate on bytes, but for example if the socket has been changed using
binmode() to operate with the :utf8 I/O layer (see the open
pragma, open), the I/O will operate on UTF-8 encoded Unicode
characters, not bytes. Similarly for the :encoding pragma:
in that case pretty much any characters can be read.