Programming Ruby

The Pragmatic Programmer's Guide
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Network and Web Libraries


Ruby provides two levels of access to network services. At a low level, you can access the basic socket support in the underlying operating system, which allows you to implement clients and servers for both connection-oriented and connectionless protocols. These are documented in the next section.

Ruby also has libraries that provide higher-level access to specific application-level network protocols, such as FTP, HTTP, and so on. These are documented starting on page 482.

Finally, the CGI libraries, documented beginning on page 497, provide server-side developers with a convenient interface for developing Web applications.

Socket-Level Access

Sockets are the endpoints of a bidirectional communications channel. Sockets may communicate within a process, between processes on the same machine, or between processes on different continents. Sockets may be implemented over a number of different channel types: Unix domain sockets, TCP, UDP, and so on. The socket library provides specific classes for handling the common transports as well as a generic interface for handling the rest. All functionality in the socket library is accessible through a single extension library. Access it using 

require 'socket'

Sockets have their own vocabulary:

domain
The family of protocols that will be used as the transport mechanism. These values are constants such as PF_INET, PF_UNIX, PF_X25, and so on.
type
The type of communications between the two endpoints, typically SOCK_STREAM for connection-oriented protocols and SOCK_DGRAM for connectionless protocols.
protocol
Typically zero, this may be used to identify a variant of a protocol within a domain and type.
hostName
The identifier of a network interface:
port
(sometimes called service) Each server listens for clients calling on one or more ports. A port may be a Fixnum port number, a string containing a port number, or the name of a service.

Sockets are children of class IO. Once a socket has been successfully opened, the conventional I/O methods may be used. However, greater efficiency is sometimes obtained by using socket-specific methods. As with other I/O classes, socket I/O blocks by default. The hierarchy of the socket classes is shown in Figure 26.1 on page 471.

For more information on the use of sockets, see your operating system documentation. You'll also find a comprehensive treatment in W. Richard Stevens, Unix Network Programming, Volumes 1 and 2 .

class BasicSocket
Parent: IO
Version: 1.6

Index:

do_not_reverse_lookup do_not_reverse_lookup= lookup_order lookup_order= close_read close_write getpeername getsockname getsockopt recv send setsockopt shutdown

BasicSocket is an abstract base class for all other socket classes.

This class and its subclasses often manipulate addresses using something called a struct sockaddr, which is effectively an opaque binary string.[In reality, it maps onto the underlying C-language struct sockaddr set of structures, documented in the man pages and in the books by Stevens.]

class methods
do_not_reverse_lookup BasicSocket.do_not_reverse_lookup -> true or false

Returns the value of the global reverse lookup flag. If set to true, queries on remote addresses will return the numeric address but not the host name.

do_not_reverse_lookup= BasicSocket.do_not_reverse_lookup = true or false

Sets the global reverse lookup flag.

lookup_order BasicSocket.lookup_order -> aFixnum

Returns the global address lookup order, one of:

Order Families Searched
LOOKUP_UNSP AF_UNSPEC
LOOKUP_INET AF_INET, AF_INET6, AF_UNSPEC
LOOKUP_INET6 AF_INET6, AF_INET, AF_UNSPEC

lookup_order= BasicSocket.lookup_order = aFixnum

Sets the global address lookup order.

instance methods
close_read aSession.close_read -> nil

Closes the readable connection on this socket.

close_write aSession.close_write -> nil

Closes the writable connection on this socket.

getpeername aSession.getpeername -> aString

Returns the struct sockaddr structure associated with the other end of this socket connection.

getsockname aSession.getsockname -> aString

Returns the struct sockaddr structure associated with aSession.

getsockopt aSession.getsockopt( level, optname ) -> aString

Returns the value of the specified option.

recv aSession.recv( len, [, flags ] ) -> aString

Receives up to len bytes from aSession.

send aSession.send( aString, flags, [, to ] ) -> aFixnum

Sends aString over aSession. If specified, to is a struct sockaddr specifying the recipient address. flags are the sum or one or more of the MSG_ options (listed on page 478). Returns the number of characters sent.

setsockopt aSession.setsockopt( level, optname, optval ) -> 0

Sets a socket option. level is one of the socket-level options (listed on page 478). optname and optval are protocol specific---see your system documentation for details.

shutdown aSession.shutdown( how=2 ) -> 0

Shuts down the receive (how == 0), or send (how == 1), or both (how == 2), parts of this socket.

class IPSocket
Parent: BasicSocket
Version: 1.6

Index:

getaddress addr peeraddr

Class IPSocket is a base class for sockets using IP as their transport. TCPSocket and UDPSocket are based on this class.

class methods
getaddress IPSocket.getaddress( hostName ) -> aString

Returns the dotted-quad IP address of hostName.

a = IPSocket.getaddress('www.ruby-lang.org')
a » "210.251.121.214"

instance methods
addr aSession.addr -> anArray

Returns the domain, port, name, and IP address of aSession as a four-element array. The name will be returned as an address if the do_not_reverse_lookup flag is true.

u = UDPSocket.new
u.bind('localhost', 8765)
u.addr » ["AF_INET", 8765, "localhost", "127.0.0.1"]
BasicSocket.do_not_reverse_lookup = true
u.addr » ["AF_INET", 8765, "127.0.0.1", "127.0.0.1"]

peeraddr aSession.peeraddr -> anArray

Returns the domain, port, name, and IP address of the peer.

class TCPSocket
Parent: IPSocket
Version: 1.6

Index:

gethostbyname new open recvfrom

t = TCPSocket.new('localhost', 'ftp')
t.gets » "220 zip.local.thomases.com FTP server (Version 6.5/OpenBSD, linux port 0.3.2) ready.\r\n"
t.close » nil

class methods
gethostbyname TCPSocket.gethostbyname( hostName ) -> anArray

Looks up hostName and returns its canonical name, an array containing any aliases, the address type (AF_INET), and the dotted-quad IP address.

a = TCPSocket.gethostbyname('ns.pragprog.com')
a » ["pragprog.com", [], 2, "216.87.136.211"]

new TCPSocket.new( hostName, port ) -> aSession

Opens a TCP connection to hostName on the port.

open TCPSocket.open( hostName, port ) -> aSession

Synonym for TCPSocket.new.

instance methods
recvfrom aSession.recvfrom( len [, flags ] ) -> anArray

Receives up to len bytes on the connection. flags is zero or more of the MSG_ options (listed on page 478). Returns a two-element array. The first element is the received data, the second is an array containing information about the peer. 

t = TCPSocket.new('localhost', 'ftp')
data = t.recvfrom(30)
data

class SOCKSSocket
Parent: TCPSocket
Version: 1.6

Index:

new open close

Class SOCKSSocket supports connections based on the SOCKS protocol.
class methods
new SOCKSSocket.new( hostName, port ) -> aSession

Opens a SOCKS connection to port on hostName.

open SOCKSSocket.open( hostName, port ) -> aSession

Synonym for SOCKSSocket.new.

instance methods
close aSession.close -> nil

Closes this SOCKS connection.

class TCPServer
Parent: TCPSocket
Version: 1.6

Index:

new open accept

A TCPServer accepts incoming TCP connections. Here is a Web server that listens on a given port and returns the time. 

require 'socket'
port = (ARGV[0] || 80).to_i
server = TCPServer.new('localhost', port)
while (session = server.accept)
  puts "Request: #{session.gets}"
  session.print "HTTP/1.1 200/OK\r\nContent-type: text/html\r\n\r\n"
  session.print "<html><body><h1>#{Time.now}</h1></body></html>\r\n"
  session.close
end

class methods
new TCPServer.new( [ hostName,] port ) -> aSession
Creates a new socket on the given interface (identified by hostName and port). If hostName is omitted, the server will listen on all interfaces on the current host (equivalent to an address of 0.0.0.0).

open TCPServer.open( [ hostName,] port ) -> aSession

Synonym for TCPServer.new.

instance methods
accept aSession.accept -> aTCPSocket

Waits for a connection on aSession, and returns a new TCPSocket connected to the caller. See the example on page 474.

class UDPSocket
Parent: IPSocket
Version: 1.6

Index:

new open bind connect recvfrom send

UDP sockets send and receive datagrams. In order to receive data, a socket must be bound to a particular port. You have two choices when sending data: you can connect to a remote UDP socket and thereafter send datagrams to that port, or you can specify a host and port for use with every packet you send. This example is a UDP server that prints the message it receives. It is called by both connectionless and connection-based clients. 

require 'socket'


$port = 4321


sThread = Thread.start do     # run server in a thread
  server = UDPSocket.open
  server.bind(nil, $port)
  2.times { p server.recvfrom(64) }
end


# Ad-hoc client
UDPSocket.open.send("ad hoc", 0, 'localhost', $port)


# Connection based client
sock = UDPSocket.open
sock.connect('localhost', $port)
sock.send("connection-based", 0)
sThread.join
produces: 
["ad hoc", ["AF_INET", 33224, "localhost", "127.0.0.1"]]
["connection-based", ["AF_INET", 33225, "localhost", "127.0.0.1"]]

class methods
new UDPSocket.new( family = AF_INET ) -> aSession

Creates an endpoint for UDP communications, optionally specifying the address family.

open UDPSocket.open( family = AF_INET ) -> aSession

Synonym for UDPSocket.new.

instance methods
bind aSession.bind( hostName, port ) -> 0

Associates the local end of the UDP connection with a given hostName and port. Must be used by servers to establish an accessible endpoint.

connect aSession.connect( hostName, port ) -> 0

Creates a connection to the given hostName and port. Subsequent UDPSocket#send requests that don't override the recipient will use this connection. Multiple connect requests may be issued on aSession: the most recent will be used by send.

recvfrom aSession.recvfrom( len [, flags ] ) -> anArray

Receives up to len bytes from aSession. flags is zero or more of the MSG_ options (listed on page 478). The result is a two-element array containing the received data and information on the sender. See the example on page 475.

send aSession.send( aString, flags ) -> aFixnum
aSession.send( aString, flags, hostName, port ) -> aFixnum

The two-parameter form sends aString on an existing connection. The four-parameter form sends aString to port on hostName.

class UNIXSocket
Parent: BasicSocket
Version: 1.6

Index:

new open addr path peeraddr recvfrom

Class UNIXSocket supports interprocess communications using the Unix domain protocol. Although the underlying protocol supports both datagram and stream connections, the Ruby library provides only a stream-based connection. 

require 'socket'


$path = "/tmp/sample"


sThread = Thread.start do        # run server in a thread
  sock = UNIXServer.open($path)
  s1 = sock.accept
  p s1.recvfrom(124)
end


client = UNIXSocket.open($path)
client.send("hello", 0)
client.close


sThread.join
produces: 
["hello", ["AF_UNIX", ""]]

class methods
new UNIXSocket.new( path ) -> aSession

Opens a new domain socket on path, which must be a pathname.

open UNIXSocket.open( path ) -> aSession

Synonym for UNIXSocket.new.

instance methods
addr aSession.addr -> anArray

Returns the address family and path of this socket.

path aSession.path -> aString

Returns the path of this domain socket.

peeraddr aSession.peeraddr -> anArray

Returns the address family and path of the server end of the connection.

recvfrom aSession.recvfrom( len [, flags ] ) -> anArray

Receives up to len bytes from aSession. flags is zero or more of the MSG_ options (listed on page 478). The first element of the returned array is the received data, and the second contains (minimal) information on the sender.

class UNIXServer
Parent: UNIXSocket
Version: 1.6

Index:

new open accept

Class UNIXServer provides a simple Unix domain socket server. See UNIXSocket for example code.

class methods
new UNIXServer.new( path ) -> aSession

Creates a server on the given path. The corresponding file must not exist at the time of the call.

open UNIXServer.open( path ) -> aSession

Synonym for UNIXServer.new.

instance methods
accept aSession.accept -> aUnixSocket

Waits for a connection on the server socket and returns a new socket object for that connection. See the example for UNIXSocket on page 476.

class Socket
Parent: BasicSocket
Version: 1.6

Index:

for_fd getaddrinfo gethostbyaddr gethostbyname gethostname getnameinfo getservbyname new open pair socketpair accept bind connect listen recvfrom

Class Socket provides access to the underlying operating system socket implementation. It can be used to provide more operating system-specific functionality than the protocol-specific socket classes, but at the expense of greater complexity. In particular, the class handles addresses using struct sockaddr structures packed into Ruby strings, which can be a joy to manipulate.

constants

Class Socket defines constants for use throughout the socket library. Individual constants are available only on architectures that support the related facility.

Types:

SOCK_DGRAM, SOCK_PACKET, SOCK_RAW, SOCK_RDM, SOCK_SEQPACKET, SOCK_STREAM.

Protocol families:

PF_APPLETALK, PF_AX25, PF_INET6, PF_INET, PF_IPX, PF_UNIX, PF_UNSPEC.

Address families:

AF_APPLETALK, AF_AX25, AF_INET6, AF_INET, AF_IPX, AF_UNIX, AF_UNSPEC.

Lookup-order options:

LOOKUP_INET6, LOOKUP_INET, LOOKUP_UNSPEC.

Send/receive options:

MSG_DONTROUTE, MSG_OOB, MSG_PEEK.

Socket-level options:

SOL_ATALK, SOL_AX25, SOL_IPX, SOL_IP, SOL_SOCKET, SOL_TCP, SOL_UDP.

Socket options:

SO_BROADCAST, SO_DEBUG, SO_DONTROUTE, SO_ERROR, SO_KEEPALIVE, SO_LINGER, SO_NO_CHECK, SO_OOBINLINE, SO_PRIORITY, SO_RCVBUF, SO_REUSEADDR, SO_SNDBUF, SO_TYPE.

QOS options:

SOPRI_BACKGROUND, SOPRI_INTERACTIVE, SOPRI_NORMAL.

Multicast options:

IP_ADD_MEMBERSHIP, IP_DEFAULT_MULTICAST_LOOP, IP_DEFAULT_MULTICAST_TTL, IP_MAX_MEMBERSHIPS, IP_MULTICAST_IF, IP_MULTICAST_LOOP, IP_MULTICAST_TTL.

TCP options:

TCP_MAXSEG, TCP_NODELAY.

getaddrinfo error codes:

EAI_ADDRFAMILY, EAI_AGAIN, EAI_BADFLAGS, EAI_BADHINTS, EAI_FAIL, EAI_FAMILY, EAI_MAX, EAI_MEMORY, EAI_NODATA, EAI_NONAME, EAI_PROTOCOL, EAI_SERVICE, EAI_SOCKTYPE, EAI_SYSTEM.

ai_flags values:

AI_ALL, AI_CANONNAME, AI_MASK, AI_NUMERICHOST, AI_PASSIVE, AI_V4MAPPED_CFG.

class methods
for_fd Socket.for_fd( anFD ) -> aSession

Wraps an already open file descriptor into a socket object.

getaddrinfo Socket.getaddrinfo( hostName, port,
[ family [ socktype [ protocol [ flags ] ] ] ] ) -> anArray

Returns an array of arrays describing the given host and port (optionally qualified as shown). Each subarray contains the address family, port number, host name, host IP address, protocol family, socket type, and protocol. 

for line in Socket.getaddrinfo('www.microsoft.com', 'http')
  puts line.join(", ")
end
produces: 
AF_INET, 80, microsoft.net, 207.46.130.149, 2, 1, 6
AF_INET, 80, microsoft.net, 207.46.131.137, 2, 1, 6
AF_INET, 80, microsoft.com, 207.46.230.218, 2, 1, 6
AF_INET, 80, microsoft.com, 207.46.230.219, 2, 1, 6
AF_INET, 80, microsoft.net, 207.46.130.14, 2, 1, 6

gethostbyaddr Socket.gethostbyaddr( addr, type=AF_INET ) -> anArray
Returns the host name, address family, and sockaddr component for the given address.

a = Socket.gethostbyname("216.87.136.211")
res = Socket.gethostbyaddr(a[3], a[2])
res.join(', ') » "pragprog.com, , 2, \330W\210\323"

gethostbyname Socket.gethostbyname( hostName ) -> anArray

Returns a four-element array containing the canonical host name, a subarray of host aliases, the address family, and the address portion of the sockaddr structure.

a = Socket.gethostbyname("216.87.136.211")
a.join(', ') » "pragprog.com, , 2, \330W\210\323"

gethostname aSession.gethostname -> aString

Returns the name of the current host.

getnameinfo Socket.getnameinfo( addr [, flags ] ) -> anArray

Looks up the given address, which may be either a string containing a sockaddr or a three- or four-element array. If sockaddr is an array, it should contain the string address family, the port (or nil), and the host name or IP address. If a fourth element is present and not nil, it will be used as the host name. Returns a canonical hostname (or address) and port number as an array.

a = Socket.getnameinfo(["AF_INET", '23', 'www.ruby-lang.org'])
a » ["helium.ruby-lang.org", "telnet"]

getservbyname Socket.getservbyname( service, proto='tcp' ) -> aFixnum

Returns the port corresponding to the given service and protocol.

Socket.getservbyname("telnet") » 23

new Socket.new( domain, type, protocol ) -> aSession

Creates a socket using the given parameters.

open Socket.open( domain, type, protocol ) -> aSession

Synonym for Socket.new.

pair Socket.pair( domain, type, protocol ) -> anArray

Returns a pair of connected, anonymous sockets of the given domain, type, and protocol.

socketpair Socket.socketpair( domain, type, protocol ) -> anArray

Synonym for Socket.pair.

instance methods
accept aSession.accept -> anArray

Accepts an incoming connection returning an array containing a new Socket object and a string holding the struct sockaddr information about the caller.

bind aSession.bind( sockaddr ) -> 0

Binds to the given struct sockaddr, contained in a string.

connect aSession.connect( sockaddr ) -> 0

Connects to the given struct sockaddr, contained in a string.

listen aSession.listen( aFixnum ) -> 0

Listens for connections, using the specified aFixnum as the backlog.

recvfrom aSession.recvfrom( len [, flags ] ) -> anArray

Receives up to len bytes from aSession. flags is zero or more of the MSG_ options. The first element of the result is the data received. The second element contains protocol-specific information on the sender.

Higher-Level Access

Ruby provides a set of classes to facilitate writing clients for:

HTTP, POP, and SMTP are layered on top of a helper class, lib/net/protocol. Although we don't document the Protocol class here, you should probably study it if you are considering writing your own network client.

class Net::FTP
Parent: Object
Version: 1.6

Index:

new open Server commands close closed? connect debug_mode debug_mode= dir getbinaryfile gettextfile lastresp list login ls mtime passive passive= putbinaryfile puttextfile resume resume= retrbinary retrlines return_code storbinary storlines welcome 

require 'net/ftp'


ftp = Net::FTP.new('ftp.netlab.co.jp')
ftp.login
files = ftp.chdir('pub/lang/ruby/contrib')
files = ftp.list('n*')
ftp.getbinaryfile('nif.rb-0.91.gz', 'nif.gz', 1024)
ftp.close

The net/ftp library implements a File Transfer Protocol (FTP) client.

constants
FTP_PORT Default port for FTP connections (21).

class methods
new FTP.new( host=nil, user=nil, passwd=nil, acct=nil) -> aSession

Creates and returns a new FTP object. If the host parameter is not nil, a connection is made to that host. Additionally, if the user parameter is not nil, the given user name, password, and (optionally) account are used to log in. See the description of FTP#login on page 484.

open FTP.open( host, user=nil, passwd=nil, acct=nil) -> aSession

A synonym for FTP.new, but with a mandatory host parameter.

instance methods
Server commands aSession.acct( account )
aSession.chdir( dir )
aSession.delete( remoteFile )
aSession.mdtm( remoteFile ) -> aString
aSession.mkdir( dir )
aSession.nlst( dir=nil ) -> anArray
aSession.rename( fromname, toname )
aSession.rmdir( dir )
aSession.pwd -> aString
aSession.size( remoteFile ) -> anInteger
aSession.status -> aString
aSession.system -> aString

Issues the corresponding server command and returns the result.

close aSession.close

Closes the current connection.

closed? aSession.closed? -> true or false

Returns true if the current connection is closed.

connect aSession.connect( host, port=FTP_PORT )

Establishes an FTP connection to host, optionally overriding the default port. If the environment variable SOCKS_SERVER is set, sets up the connection through a SOCKS proxy. Raises an exception (typically Errno::ECONNREFUSED) if the connection cannot be established.

debug_mode aSession.debug_mode -> true or false

Returns the current debug mode.

debug_mode= aSession.debug_mode = true or false

If the debug mode is true, all traffic to and from the server is written to $stdout.

dir aSession.dir( [pattern]* ) -> anArray
aSession.dir( [pattern]* ) {| line | block }

Synonym for FTP#list.

getbinaryfile aSession.getbinaryfile( remotefile, localfile, blocksize, callback=nil)
aSession.getbinaryfile( remotefile, localfile, blocksize ) {| data | block }

Retrieves remotefile in binary mode, storing the result in localfile. If callback or an associated block is supplied, calls it, passing in the retrieved data in blocksize chunks.

gettextfile aSession.gettextfile( remotefile, localfile, callback=nil)
aSession.gettextfile( remotefile, localfile ) {| data | block }

Retrieves remotefile in ASCII (text) mode, storing the result in localfile. If callback or an associated block is supplied, calls it, passing in the retrieved data one line at a time.

lastresp aSession.lastresp -> aString

Returns the host's last response.

list aSession.list( [pattern]* ) -> anArray
aSession.list( [pattern]* ) {| line | block }

Fetches a directory listing of files matching the given pattern(s). If a block is associated with the call, invokes it with each line of the result. Otherwise, returns the result as an array of strings.

login aSession.login( user="anonymous", passwd=nil, acct=nil ) -> aString

Logs into the remote host. aSession must have been previously connected. If user is the string ``anonymous'' and the password is nil, a password of user@host is synthesized. If the acct parameter is not nil, an FTP ACCT command is sent following the successful login. Raises an exception on error (typically Net::FTPPermError).

ls aSession.ls( [pattern]* ) -> anArray
aSession.ls( [pattern]* ) {| line | block }

Synonym for FTP#list.

mtime aSession.mtime( remoteFile, local=false ) -> aTime

Returns the last-modified time of remoteFile, interpreting the server's response as a GMT time if local is false, or as a local time otherwise.

passive aSession.passive -> true or false

Returns the state of the passive flag.

passive= aSession.passive = true or false

Puts the connection into passive mode if true.

putbinaryfile aSession.putbinaryfile( localfile, remotefile, blocksize, callback=nil)
aSession.putbinaryfile( localfile, remotefile, blocksize ) {| data | block }

Transfers localfile to the server in binary mode, storing the result in remotefile. If callback or an associated block is supplied, calls it, passing in the transmitted data in blocksize chunks.

puttextfile aSession.puttextfile( localfile, remotefile, callback=nil)
aSession.puttextfile( localfile, remotefile, blocksize ) {| data | block }

Transfers localfile to the server in ASCII (text) mode, storing the result in remotefile. If callback or an associated block is supplied, calls it, passing in the transmitted data one line at a time.

resume aSession.resume -> true or false

Returns the status of the resume flag (see FTP#resume=). Default is false.

resume= aSession.resume=aBoolean

Sets the status of the resume flag. When resume is true, partially received files will resume where they left off, instead of starting from the beginning again. This is done by sending a REST command (RESTart incomplete transfer) to the server.

retrbinary aSession.retrbinary( cmd, blocksize ) {| data | block }

Puts the connection into binary (image) mode, issues the given command, and fetches the data returned, passing it to the associated block in chunks of blocksize characters. Note that cmd is a server command (such as ``RETR myfile'').

retrlines aSession.retrlines(cmd) {| line | block }

Puts the connection into ASCII (text) mode, issues the given command, and passes the resulting data, one line at a time, to the associated block. If no block is given, prints the lines. Note that cmd is a server command (such as ``RETR myfile'').

return_code aSession.return_code -> aFixnum

Returns the return code from the last operation.

storbinary aSession.storbinary( cmd, fileName, blocksize, callback=nil)
aSession.storbinary( cmd, fileName, blocksize ) {| data | block }

Puts the connection into binary (image) mode, issues the given server-side command (such as ``STOR myfile''), and sends the contents of the file named fileName to the server. If the optional block is given, or if the callBack parameter is a Proc, also passes it the data, in chunks of blocksize characters.

storlines aSession.storlines( cmd, fileName, callback=nil)
aSession.storlines( cmd, fileName ) {| data | block }

Puts the connection into ASCII (text) mode, issues the given server-side command (such as ``STOR myfile''), and sends the contents of the file named fileName to the server, one line at a time. If the optional block is given, or if the callBack parameter is a Proc, also passes it the lines.

welcome aSession.welcome -> aString

Returns the host's welcome message.

class Net::HTTP
Parent: Net::Protocol
Version: 1.6

Index:

new port start get head post start 

require 'net/http'


h = Net::HTTP.new('www.pragmaticprogrammer.com', 80)
resp, data = h.get('/index.html', nil )
puts "Code = #{resp.code}"
puts "Message = #{resp.message}"
resp.each {|key, val| printf "%-14s = %-40.40s\n", key, val }
p data[0..55]
produces: 
Code = 200
Message = OK
last-modified  = Wed, 29 May 2002 11:08:01 GMT
connection     = close
content-type   = text/html
etag           = "804d98-255c-3cf4b691"
date           = Sun, 09 Jun 2002 05:15:10 GMT
server         = Rapidsite/Apa/1.3.20 (Unix) FrontPage/4.
content-length = 9564
accept-ranges  = bytes
"<!DOCTYPE HTML PUBLIC \"-//W3C//DTD HTML 4.0 Transitional"

The net/http library provides a simple client to fetch headers and Web page contents using the HTTP protocol.

The get, post, and head requests raise exceptions on any error, including some HTTP status responses that would normally be considered recoverable. There are two ways of handling these.

  1. Each method has a corresponding version get2, post2, or head2 that does not raise an exception. These versions are documented in the source.
  2. Recoverable errors raise a Net::ProtoRetriableError exception. This exception contains a data attribute containing the response returned by the server.

The code below illustrates the handling of an HTTP status 301, a redirect. It uses Tomoyuki Kosimizu's URI package, available in the RAA. 

h = Net::HTTP.new(ARGV[0] || 'www.ruby-lang.org', 80)
url = ARGV[1] || '/'


begin
  resp, data = h.get(url, nil) { |a| }
rescue Net::ProtoRetriableError => detail
  head = detail.data


  if head.code == "301"
    uri = URI.create(head['location'])


    host = uri['host']
    url  = uri['path']
    port = uri['port']


    h.finish
    h = Net::HTTP.new(host, port)


    retry
  end
end

class methods
new Net::HTTP.new( host='localhost', port=80, proxy=nil, proxy_port=nil ) -> aSession

Creates and returns a new HTTP object. No connection is made until HTTP#start is called.

port Net::HTTP.port -> aFixnum

Returns the default HTTP port (80).

start Net::HTTP.start( host=nil, port=80 )
Net::HTTP.start( host=nil, port=80 ) {| aSession | block }

Equivalent to Net::HTTP.new(host, port).start.

instance methods
get aSession.get( path, headers=nil, dest="" ) -> anArray
aSession.get( path, headers=nil) {| result | block }

-> anArray

Retrieves headers and content from the specified path on the host specified when aSession was created. If specified, the headers parameter is a Hash containing additional header names and values to be sent with the request. The method returns a two-element array. The first element is an HTTPResponse object (documented in the next section). The second element is the page's content. The page's content is also passed to the << method of the dest parameter, or to the block if specified. This result is built network block by network block, not line by line. An exception is raised if an error is encountered. Multiple get calls may be made on aSession. Unless Protocol#finish is explicitly called, the connection will use the HTTP/1.1 keep-alive protocol, and will not close between requests.

head aSession.head( path, headers=nil ) -> aHash

Retrieves headers from the specified path on the host specified when aSession was created. If specified, the headers parameter is a hash containing additional header names and values to be sent with the request. The method returns a hash of received headers. An exception is raised if an error is encountered. Multiple head calls may be made on aSession.

post aSession.post( path, data, headers=nil, dest="" ) -> anArray
aSession.post( path, data, headers=nil ) {| result | block } -> anArray

Sends data to path using an HTTP POST request. headers is a hash containing additional headers. Assigns the result to data or to the block, as for Net_HTTP#get. Returns a two-element array containing an HTTPResponse object and the reply body.

start aSession.start
aSession.start {| aSession | block }

Establishes a connection to the host associated with aSession. (start is actually a method in Net::Protocol, but its use is required in HTTP objects.) In the block form, closes the session at the end of the block.

class Net::HTTPResponse
Parent:
Version: 1.6

Index:

[ ] [ ]= code each key? message

Represents an HTTP response to a GET or POST request.

instance methods
[ ] aSession[ aKey ] -> aString

Returns the header corresponding to the case-insensitive key. For example, a key of ``Content-type'' might return ``text/html''.

[ ]= aSession[ aKey ] = aString

Sets the header corresponding to the case-insensitive key.

code aSession.code -> aString

Returns the result code from the request (for example, ``404'').

each aSession.each {| key, val | block }

Iterates over all the header key-value pairs.

key? aSession.key?( aKey ) -> true or false

Returns true only if a header with the given key exists.

message aSession.message -> aString

Returns the result message from the request (for example, ``Not found'').

class Net::POP
Parent: Net::Protocol
Version: 1.6

Index:

new each finish mails start 

require 'net/pop'
pop = Net::POP3.new('server.ruby-stuff.com')
pop.start('user', 'secret') do |pop|
  msg = pop.mails[0]


  # Print the 'From:' header line
  puts msg.header.split("\r\n").grep(/^From: /)


  # Put message to $stdout (by calling <<)
  puts "\nFull message:\n"
  msg.all($stdout)
end
produces: 
From: dummy msg for Andy


Full message:
From: dummy msg for Andy
looks-better: on dave's box


That's all folks!

The net/pop library provides a simple client to fetch and delete mail on a Post Office Protocol (POP) server.

The class Net::POP3 is used to access a POP server, returning a list of Net::POPMail objects, one per message stored on the server. These POPMail objects are then used to fetch and/or delete individual messages. The library also provides an alternative to the POP3 class that performs APOP authentication.

class methods
new HTTP.new( host='localhost', port=110 ) -> aSession

Creates and returns a new POP3 object. No connection is made until POP3#start is called.

instance methods
each aSession.each {| popmail | block }

Calls the associated block once for each e-mail stored on the server, passing in the corresponding POPMail object.

finish aSession.finish -> true or false

Closes the pop connection. Some servers require that a connection is closed before they honor actions such as deleting mail. Returns false if the connection was never used.

mails aSession.mails -> anArray

Returns an array of POPMail objects, where each object corresponds to an e-mail message stored on the server.

start aSession.start( user, password )
aSession.start( user, password ) {| pop | block }

Establishes a connection to the pop server, using the supplied username and password. Fetches a list of mail held on the server, which may be accessed using the POP3#mails and POP3#each methods. In block form, passes aSession to the block, and closes the connection using finish when the block terminates.

class Net::APOP
Parent: Net::POP3
Version: 1.6

Index:

start

instance methods
start aSession.start( user, password )

Establishes a connection to the APOP server.

class Net::POPMail
Parent: Object
Version: 1.6

Index:

all delete delete! header size top uidl

instance methods
all aSession.all -> aString
aSession.all( dest )
aSession.all {| aString | block }

Fetches the corresponding e-mail from the server. With no argument or associated block, returns the e-mail as a string. With an argument but no block, appends the e-mail to dest by invoking dest << for each line in the e-mail. With an associated block, invokes the block once for each line in the e-mail.

delete aSession.delete

Deletes the e-mail from the server.

delete! aSession.delete!

Synonym for POPMail#delete.

header aSession.header -> aString

Returns the header lines for the corresponding e-mail message.

size aSession.size -> aFixnum

Returns the size in bytes of the corresponding e-mail.

top aSession.top( lines ) -> aString

Returns the header lines, plus lines message lines for the corresponding e-mail message.

uidl aSession.uidl -> aString

Returns the server-specific unique identifier for the corresponding e-mail.

class Net::SMTP
Parent: Net::Protocol
Version: 1.6

Index:

new start ready sendmail start 

require 'net/smtp'


# --- Send using class methods
msg = [ "Subject: Test\n", "\n", "Now is the time\n" ]
Net::SMTP.start do |smtp|
  smtp.sendmail( msg,  'dave@localhost', ['dave'] )
end


# --- Send using SMTP object and an adaptor
smtp = Net::SMTP.new
smtp.start('pragprog.com')
smtp.ready('dave@localhost', 'dave') do |a|
  a.write "Subject: Test1\r\n"
  a.write "\r\n"
  a.write "And so is this"
end

The net/smtp library provides a simple client to send electronic mail using the Simple Mail Transfer Protocol (SMTP).
class methods
new Net::SMTP.new( server='localhost', port=25 ) -> aSession

Returns a new SMTP object connected to the given server and port.

start Net::SMTP.start( server='localhost', port=25, domain=ENV['HOSTNAME'], acct=nil, passwd=nil, authtype=:cram_md5 ) -> aSession
Net::SMTP.start( server='localhost', port=25, domain=ENV['HOSTNAME'], acct=nil, passwd=nil, authtype=:cram_md5 ) {| smtp | block }

Equivalent to Net::SMTP.new(server, port).start(...). For an explanation of the remainder of the parameters, see the instance method Net_SMTP#start. Creates a new SMTP object. The domain parameter will be used in the initial HELO or EHLO transaction with the SMTP server. In the block form, the smtp object is passed into the block. When the block terminates, the session is closed.

instance methods
ready aSession.ready( from, to ) {| anAdaptor | block }

Equivalent to sendmail(from, to) { ...}. Sends header and body lines to the sendmail server. The from parameter is used as the sender's name in the MAIL FROM: command, and the to is either a string or an array of strings containing the recipients for the RCPT TO: command. The block is passed an adaptor object. Lines are sent to the server by calling the adaptor's write method. The terminating '.' and QUIT are sent automatically.

sendmail aSession.sendmail( src, from, to )

Sends header and body lines to the sendmail server. The from parameter is used as the sender's name in the MAIL FROM: command, and to is either a string or an array of strings containing the recipients for the RCPT TO: command. Lines to be sent are fetched by invoking src .each. The terminating '.' and QUIT are sent automatically.

start aSession.start( domain=ENV['HOSTNAME'], acct=nil, passwd=nil, authtype=:cram_md5 ) -> true or false
aSession.start( domain=ENV['HOSTNAME'], acct=nil, passwd=nil, authtype=:cram_md5 ) {| smtp | block } -> true or false

Starts an SMTP session by connecting to the given domain (host). If acct and passwd are given, authentication will be attempted using the given authentication type (:plain or :cram_md5). If a block is supplied, it will be invoked with aSession as a parameter. The connection will be closed when the block terminates.

class Net::Telnet
Parent: [Socket]
Version: 1.6

Index:

new binmode binmode= cmd login print telnetmode telnetmode= waitfor write

Connect to a localhost, run the ``date'' command, and disconnect.

require 'net/telnet'
tn = Net::Telnet.new({})
tn.login "guest", "secret"
tn.cmd "date" » "date\r\nSun Jun  9 00:15:20 CDT 2002\n\r> "

Monitor output as it occurs. We associate a block with each of the library calls; this block is called whenever data becomes available from the host. 

require 'net/telnet'


tn = Net::Telnet.new({})     { |str| print str }
tn.login("guest", "secret")  { |str| print str }
tn.cmd("date")  { |str| print str }
produces: 
Trying localhost...
Connected to localhost.
Welcome to SuSE Linux 7.1 (i386) - Kernel 2.4.0-64GB-SMP (8).


zip login: guest
Password:
Last login: Sun Jun  9 00:15:19 from localhost
/etc/zshrc: setopt: no such option: histexpiredupsfirst [31]

> date
Sun Jun  9 00:15:20 CDT 2002

>

Get the time from an NTP server. 

require 'net/telnet'
tn = Net::Telnet.new('Host'       => 'time.nonexistent.org',
                     'Port'       => 'time',
                     'Timeout'    => 60,
                     'Telnetmode' => false)
atomicTime = tn.recv(4).unpack('N')[0]
puts "Atomic time: " + Time.at(atomicTime - 2208988800