Sockets

Sockets are the low-level links that enable Internet conversations and many other network services. There are a many functions that deal with sockets. Fortunately, you don't normally need to deal with them all. A small subset is all you need to get started. This section will focus in on those aspects of sockets that are useful in Perl. There will be whole areas of sockets that are not dealt with here.

A small selection of useful Perl socket functions is given below:

accept(NEWSOCKET, SOCKET)

-- Accepts a socket connection from clients waiting for a connection. The original socket, SOCKET, is left along, and a new socket is created for the remote process to talk with. SOCKET must have already been opened using the socket() function. Returns true if it succeeded, false otherwise.

bind(SOCKET, PACKED_ADDRESS)

-- Binds a network address to the socket handle. Returns true if it succeeded, false otherwise.

connect(SOCKET, PACKED_ADDRESS)

-- Attempts to connect to a socket. Returns true if it succeeded, false otherwise. getpeername(SOCKET)Returns the packed address of the remote side of the connection. This function can be used to reject connections for security reasons, if needed.

getsockname(SOCKET)

-- Returns the packed address of the local side of the connection.

getsockopt(SOCKET, LEVEL, OPTNAME)

-- Returns the socket option requested, or undefined if there is an error.

listen(SOCKET, QUEUESIZE)

-- Creates a queue for SOCKET with QUEUESIZE slots. Returns true if it succeeded, false otherwise.

recv(SOCKET, BUFFER, LEN, FLAGS)

-- Attempts to receive LENGTH bytes of data into a buffer from SOCKET. Returns the address of the sender, or the undefined value if there's an error. BUFFER will be grown or shrunk to the length actually read. However, you must initalize BUFFER before use. For example my($buffer) = '';.

select(RBITS, WBITS, EBITS, TIMEOUT)

-- Examines file descriptors to see if they are ready or if they have exception conditions pending.

send(SOCKET, BUFFER, FLAGS, [TO])

-- Sends a message to a socket. On unconnected sockets you must specify a destination (the TO parameter). Returns the number of characters sent, or the undefined value if there is an error.

setsockopt(SOCKET, LEVEL, OPTNAME, OPTVAL)

-- Sets the socket option requested. Returns undefined if there is an error. OPTVAL may be specified as undefined if you don't want to pass an argument.

shutdown(SOCKET, HOW)

-- Shuts down a socket connection in the manner indicated by HOW. If HOW = 0, all incoming information will be ignomiles. If HOW = 1, all outgoing information will be stopped. If HOW = 2, then both sending and receiving is disallowed.

socket(SOCKET, DOMAIN,TYPE, PROTOCOL)

-- Opens a specific TYPE of socket and attaches it to the name SOCKET. Returns true if successful, false if not.

socketpair(SOCK1, SOCK2, DOMAIN, TYPE, PROTO)

- Creates an unnamed pair of sockets in the specified domain, of the specified type. Returns true if successful, false if not.

Note

If you are interested in knowing everything about sockets, you need to get your hands on some UNIX documentation. The Perl set of socket functions are pretty much a duplication of those available using the C language under UNIX. Only the parameters are different because Perl data structures are handled differently. You can find UNIX documentation at http://www.delorie.com/gnu/docs/ on the World Wide Web.