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Synchronous I/O engine
The following code implements network transport that performs synchronous,
blocking I/O over a single BSD socket. It is intended to serve as a
network transport for SNMP messages, within a synchronous SNMP entity
process, over a TCP/IP network.
The pysnmp.mapping.udp.role module defines the following
- class manager([dst[,iface]])
Returns a new instance of manager class, representing
network client (SNMP manager) optionally connected to a network server
running at dst address. The dst argument,
whenever given, must follow the socket module notation --
('hostname', port) where hostname is a
string and port is an integer.
The default for dst is None what means no default destination,
so user would unconditionally have to specify destination to each
manager.send() method (see below).
Once a default dst is specified, specific destination
may not be given to the manager.send() method.
The iface parameter, if given, specifies the interface and
port on local machine to bind() to. This argument must also
follow the socket module notation. All further requests
would then be originated from the given interface/port (for example,
The default for iface is ('0.0.0.0', 0) what stands for
binding to a primary interface at the local machine.
- class agent([(cb_fun, cb_ctx)[, ifaces]])
Returns a new instance of agent class, representing
network server optionally bound to specific network interfaces/ports
ifaces at the local machine. The ifaces
argument, whenever given, must be a list of ('ifacename',
port) tuples given in socket module
The optional cb_fun and cb_ctx parameters
may be used on class instaniation to specify default user callback function
to be invoked on message receiption. A reference to user-specific data
(context) may be passed as cb_ctx parameter.
The cb_fun, if given, must match the following prototype:
- cb_fun(cb_ctx, (question, src))
Where question is an octet-string, as received from network,
and src is question's source address given in socket
The callback function is expected to return a tuple of
(answer, dst), where
answer (string) is the data item to be replied back to
manager by address dst (given in socket
The default for the ifaces is to listen on the loopback
interface, port 161/UDP, so the default value is [('127.0.0.1', 161)].
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.
Methods of the above classes may raise exceptions based on
error.SnmpOverUdpError base class.