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<HTML>
<HEAD>
<TITLE>PySNMP: I/O engine: Single-session</TITLE>
</HEAD>
<BODY BGCOLOR="#ffffff" TEXT="#000000"
LINK="#0000bb" VLINK="#551a8b" ALINK="#ff0000">
<H3>
Single-session, blocking I/O engine
</H3>
<P>
The <STRONG>pysnmp.role</STRONG> module defines <STRONG>manager</STRONG> and
<STRONG>agent</STRONG> classes, representing SNMP manager and agent roles in
a SNMP system. These classes implement network client (manager) and server
(agent) respectively, that do blocking I/O over a single BSD socket. They
are intended to serve as a network transport for SNMP messages, within a
synchronous SNMP entity process, over a TCP/IP network.
</P>
<P>
The <STRONG>pysnmp.role</STRONG> code is a pure network transport facility --
it deals with abstract data items and has nothing to know about SNMP context.
In order to build a complete SNMP entity, a SNMP message processing code
should be used along. See SNMP protocol modules (<A HREF="v2c.html">v2c</A>,
<A HREF="v1.html">v1</A>) for that.
</P>
<P>
Consequently, any custom, task specific transport may be employed instead in
user applications in conjunction with the SNMP protocol modules.
</P>
<P>
The <STRONG>pysnmp.role</STRONG> module defines the following items:
</P>
<DL>
<DT>class <STRONG>manager</STRONG>([<STRONG>dst</STRONG>[,<STRONG>iface</STRONG>]])</DT>
<DD>
<P>
Returns a new instance of <STRONG>manager</STRONG> class, representing
network client optionally connected to a network server running at
<STRONG>dst</STRONG> address. The <STRONG>dst</STRONG> argument, whenever
given, must follow the <STRONG>socket</STRONG> module notation --
('<STRONG>hostname</STRONG>', <STRONG>port</STRONG>) where hostname a string
and port is an integer.
</P>
<P>
The default for <STRONG>dst</STRONG> is None what means no default destination,
so user would unconditionally have to specify destination to each
<STRONG>manager.send()</STRONG> method (see below).
</P>
<P>
Once a default <STRONG>dst</STRONG> is specified, specific destination
may not be given to the <STRONG>manager.send()</STRONG> method.
</P>
<P>
The <STRONG>iface</STRONG> parameter, if given, specifies the interface and
port on local machine to <STRONG>bind()</STRONG> to. This argument must also
follow the <STRONG>socket</STRONG> module notation. All further requests
would then be originated from the given interface/port (for example,
('127.0.0.1', 0)).
</P>
<P>
The default for <STRONG>iface</STRONG> is ('0.0.0.0', 0) what stands for binding
to a primary interface at the local machine.
</P>
</DD>
<DT>class <STRONG>agent</STRONG>([<STRONG>ifaces</STRONG>])</DT>
<DD>
<P>
Returns a new instance of <STRONG>agent</STRONG> class, representing
network server optionally bound to specific network interfaces/ports
<STRONG>ifaces</STRONG> at the local machine. The <STRONG>ifaces</STRONG>
argument, whenever given, must be a list of ('<STRONG>ifacename</STRONG>',
<STRONG>port</STRONG>) tuples (<STRONG>socket</STRONG> module notation).
</P>
<P>
The default for the <STRONG>ifaces</STRONG> is to listen on the loopback
interface, port 161/UDP, so the default value is [('127.0.0.1', 161)].
</P>
<P>
Be aware that for a UNIX process to bind(2) to a low port, such as 161 (that
is less than 1024), a superuser privelege is required. Since running
scripts under superuser privelege is not particular secure in UNIX environment,
binding to a non-priveleged port is therefore strongly recommended.
</P>
</DD>
</DL>
<DL>
<DT>exception <STRONG>Error</STRONG></DT>
<DD>
<P>
Exception raised on any error in the <STRONG>pysnmp.role</STRONG> module
and its derivatives. This exception class is a subclass of the
<STRONG>error.General</STRONG> class.
</P>
<P>
See documentation on the <A HREF="error.html">error.General</A> base class for
usage details.
</P>
</DD>
</DL>
<P>
The following exceptions are derived from this class:
</P>
<DL>
<DT>exception <STRONG>BadArgument</STRONG></DT>
<DD>
<P>
Bad parameters given.
</P>
</DD>
</DL>
<DL>
<DT>exception <STRONG>NetworkError</STRONG></DT>
<DD>
<P>
Besides being used to report various network related problems, this class also
serves as a base class for a few specific exceptions (read on).
</P>
</DD>
</DL>
<P>
The following exceptions are derived from the <STRONG>NetworkError</STRONG> class:
</P>
<DL>
<DT>exception <STRONG>NoResponse</STRONG></DT>
<DD>
<P>
No response arrived before timeout.
</P>
</DD>
</DL>
<DL>
<DT>exception <STRONG>NoRequest</STRONG></DT>
<DD>
<P>
No request came before timeout.
</P>
</DD>
</DL>
<HR><STRONG>Subsections</STRONG>
<P>
<UL>
<LI>Objects of the <A HREF="role-manager-objects.html">
<STRONG>role.manager</STRONG></A> class
<LI>Objects of the <A HREF="role-agent-objects.html">
<STRONG>role.agent</STRONG></A> class
</UL>
<HR>
<ADDRESS>
ilya@glas.net
</ADDRESS>
</BODY>
</HTML>
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