--- Generic, TCP and unix sockets

bind(addr)
	create a server socket, bind it, then listen. 
	arguments: raw address, as a string
	return the server socket file descriptor (as an integer),  
	or nil, error msg

accept(fd)
	accept incoming connections on a server socket
	fd: the server socket file descriptor (as an integer)
	return the client socket file descriptor (as an integer) and
	the raw client address as a string,  or nil, error msg
	
connect(addr)
	connect to a server
	argument: the server raw address, as a string
	return the connection socket fd (as an integer), 
	or nil, error msg
	
read(fd [, timeout])
	read bytes from a socket
	fd: the socket descriptor (as an integer)
	timeout: an integer number of milliseconds (defaults to 10,000 - see
	  DEFAULT_TIMEOUT in minisock.c)
	the function reads up to BUFSIZE bytes (read uses an internal buffer
	which is BUFSIZE bytes large - default BUFSIZE value is 4,096)
	return the bytes read as a string, or (nil, error msg) on error or 
	timeout. The error msg includes the value of 'errno'.
	
write(fd, s [, idx, n])
	write bytes from a string to a socket
	fd: the socket descriptor (as an integer)
	s: the string containing the bytes to send
	idx: integer index in s. The bytes to send start in s at idx
	n: number of bytes to send (if too large, n is adjusted to the number
	   of bytes remaining in string s at idx)
	idx and n are optional. If not present they are assumed to be 1 and 
	the number of bytes remaining in string s at idx.
	return the number of bytes sent, or (nil error msg). In case of 
	write error, the error msg includes the value of 'errno'
	
close(fd)
	close a socket 
	fd: the socket file descriptor (as integer)
	return true on success or nil, errmsg	


--- UDP sockets

udpsocket([addr])
	create a UDP Datagram socket. Optionnally bind it if an address 
	is provided.
	addr: the server sockaddr as a binary string. 
	addr is optional. if addr is null or empty, an AF_INET socket 
	is created and not bound. if addr is "\x0a", an AF_INET6 
	socket is created and not bound. if addr length is > 1, 
	the socket is created and bound.
	return the socket file descriptor as integer or nil, errmsg

sendto(fd, addr, msg)
	send a message on a socket
	fd: integer - socket descriptor
	addr: raw address (sockaddr) of the recipient
	msg: string to send
	return number of bytes sent or nil, errmsg

recvfrom(fd [, timeout])
	receive message from a socket file descriptor
	Lua args:  
	   socket fd: integer
	   optional timeout: integer (in milliseconds). defaults to
	   DEFAULT_TIMEOUT (10,000 i.e. 10 seconds)
	reads at most UDPMAXSIZE bytes (2,048) 
	return the received message as a string, and the sender 
	raw address, or (nil, error msg) on error or timeout


--- Information

getsockname(fd)
	get the address a socket is bound to
	fd: the socket file descriptor (as integer)
	return the raw client address as a string,  or nil, errmsg
	
getpeername(fd)
	get the address of the peer a socket is connected to
	fd: the socket file descriptor (as integer)
	return the raw client address as a string,  or nil, errmsg	

getaddrinfo(hostname [, port])
	get a list of addresses corresponding to a hostname and port
	return the list of ip addresses as a Lua table

getnameinfo(addr [, numeric_host])
	converts a raw address into a host and port
	addr: a raw address (sockaddr) as returned by bind, connect, 
    accept, getaddrinfo.
	numeric_host: if true, the function returns a numeric IP address for 
	the host.
	return hostname-or-IP-address, port (port is returned as an integer)


--- Misc

msleep(n)
	suspend the execution of the calling thread for n milliseconds
	(it uses the linux nanosleep() function)
	return value: true on success, or (nil, error msg)