1Net::SSH::Perl::SubsystUesme:r:SCeornvterri(b3u)ted PerlNeDto:c:uSmSeHn:t:aPteiroln::Subsystem::Server(3)
2
6 Net::SSH::Perl::Subsystem::Server - Server infrastructure for SSH
7 subsystems
8
10 use Net::SSH::Perl::Subsystem::Server;
11 use base qw( Net::SSH::Perl::Subsystem::Server );
12 use constant MSG_FOO => 1;
14 sub init {
16 my $ss = shift;
17 $ss->SUPER::init(@_);
18 $ss->register_handler(MSG_FOO, \&handle_foo);
20 }
21 sub handle_foo {
23 my $ss = shift;
24 my($msg) = @_;
25 print "Got MSG_FOO message!\n";
26 }
27
29 Net::SSH::Perl::Subsystem::Server is a generic subclass that can be
30 used to build servers for SSH-2 subsystems. A subsystem is a network
31 protocol that runs on top of a secure, encrypted SSH connection between
32 two machines: it allows the user and developer to build a secure
33 network protocol without worrying about the details of that security,
34 because it inherits the secure tunnel from SSH.
35 Subsystem::Server provides basic functionality needed by all subsystem
37 servers. A subsystem daemon is started up by the sshd when a request
38 comes in for that subsystem; sshd and the subsystem daemon then talk to
39 each other through pipes, and data that the daemon wishes to send to
40 the subsystem client is sent over the network through the SSH secure
41 tunnel. Subsystem::Server handles the talking to the sshd, and lets the
42 application developer focus on designing the network protocol and
43 handling requests from the subsystem client.
44
46 Net::SSH::Perl::Subsystem::Server is meant to be used as a base class
47 for subsystem servers. With that in mind, general usage should follow
48 the example above in the SYNOPSIS:
49 • Initialization
51 If you want your subclass to do anything, you'll want to override
53 the init method so that you can set up handlers for specific types
54 of messages from the subsystem client. For each message type, you
55 need to associate the type with a subroutine reference that will be
56 invoked when a message of that type is received by the core server.
57 You do this by calling the register_handler method (see below).
58 • Message Handling
60 When the core server receives new messages from the client, it
62 grabs the first byte from the incoming stream; the first byte is a
63 packed 8-bit integer representing the type of the message. This
64 identifier is used to look up the message handler to handle this
65 particular type of message.
66 These are the public methods in which your subclass will be most
68 interested:
69 $ss->init(%args)
71 Initializes the subsystem server object. This is where you'll want to
72 set up your message handlers (using register_handler) and perhaps
73 perform any other protocol-specific initialization.
74 Make sure that your init method returns the $ss object on success;
76 failure to return init should be an indication of failure to calling
77 code.
78 %args can contain whatever you like it to contain. The base class
80 Net::SSH::Perl::Subsystem::Server takes these parameters in %args:
81 • Log
83 The location of a file on disk where you can write messages to be
85 logged. This is the file to which messages sent to the log method
86 (below) will be written.
87 This is an optional argument; if not specified, no log file will be
89 used, and calls to log will be silently ignored.
90 $ss->register_handler($type, $code)
92 Configures the subsystem server $ss such that any message sent from the
93 client whose type is $type will automatically invoke the subroutine
94 reference $code. This is how you build protocol-specific functionality
95 into your subsystem: you associate message types with methods.
96 The subroutine reference $code will be invoked and given two arguments:
98 $ss, the instance of the subsystem server that is blessed into your
99 subclass, and $msg, a buffer in the class Net::SSH::Perl::Buffer
100 (although you can choose a different buffer class--see buffer_class,
101 below).
102 $ss->send_msg($msg)
104 Sends the message $msg to the client. Or, in more technical terms, adds
105 the message $msg to the server's output queue, to be written back to
106 the client the next time through the select loop.
107 $msg should be a buffer in the class Net::SSH::Perl::Buffer (although
109 you can choose a different buffer class--see buffer_class, below).
110 $ss->serve
112 Enters the select loop, waiting for requests from the client. Users of
113 your class should call this method when they're ready to start serving
114 clients.
115 $ss->log($message)
117 Writes the log message $message to the log file, if one was specified
118 as the Log argument to init (or, rather, to the constructor).
119 If a log file was not specified, returns silently.
121 $ss->buffer_class
123 By default, messages are represented by Net::SSH::Perl::Buffer objects.
124 You can alter this by overriding the buffer_class method; it should
125 return the name of an alternate class. Be aware that this alternate
126 class must conform to the interface used by Net::SSH::Perl::Buffer, so
127 you may be best off subclassing that class and adding in your own
128 functionality.
129
131 It should be noted that the external interface (API) to this module is
132 alpha, and could change.
133
135 Please see the Net::SSH::Perl manpage for author, copyright, and
136 license information.
137perl v5.34.0 2021-07-2N2et::SSH::Perl::Subsystem::Server(3)