Python basic teaching UDP port scan

I. Overview
Task Description:
Develop a program to obtain a list of host IP addresses for the SNMP service on the LAN and write the corresponding files for use by other programs.
Background knowledge:
SNMP is UDP-based, and the standard SNMP service uses 161 and 162 ports.
Ideas:
1, get the local area online host list;
2, get the SNMP port of each host (for example, 161) to open the State;
3. Write specific files in a specific format.
Only the first two steps are implemented here.

Second, NMAP implementation
1. Installing Nmap
Linux platforms (CentOS for example):

Yum Install Nmap-y
Widows platform (download address):
Http://nmap.org/download.html#windows

2. Get a list of online hosts
Take 192.168.1.0/24 network segment as an example:

NMAP-SN 192.168.1.0/24
Or specify an IP range scan:

NMAP-SN 192.168.1.1-254
Parameter explanation:
-sn:ping Scan, only host discovery, no port scan.

3. Get the host port open condition
Taking 192.168.1.100 as an example

Nmap-p 161-su 192.168.1.100
Parameter explanation:

-P 161: Scan 161 ports
-SU: for UDP scanning
Nmap returns results:

Open: Opening
Closed: Off
Filtered: Port blocked by firewall ids/ips, unable to determine its status
Unfiltered: The port is not blocked, but it needs to be further determined if it is open
Open|filtered: The port is open or blocked
Closed|filtered: The port is closed or blocked
4, Nmap Shortcut

Scan the 161 ports of the 192.168.1.0/24 network segment as follows:
Nmap-p 161-su 192.168.1.0/24
Third, Python implementation (with Python-nmap)
The return value of Nmap has a lot of data and needs to be interpreted by its own program, such as the result of scanning the 161 port of 192.168.1.100:

Nmap Scan Report for 192.168.1.100
Host is up (0.00024s latency).
PORT State SERVICE
161/UDP closed SNMP
MAC address:10:bf:5a:6a:ba:48 (Unknown)
There is a Python parsing library, which is developed by invoking the NMAP command and parsing the results, returning the data structures that Python can recognize:
Name: Python-nmap
Url:http://xael.org/norman/python/python-nmap/python-nmap-0.1.4.tar.gz

Example (scan SNMP service on LAN for each host):

The code is as follows:

#! /usr/bin/python

Import Nmap
NM = Nmap. Portscanner ()
Nm.scan (hosts= ' 192.168.1.0/24 ', arguments= '-P 161-su ')
Hosts_list = [(x, Nm[x][u ' UDP '][161][' state ') ") for x in Nm.all_hosts ()]
For host, status in Hosts_list:
Print (' {0}:{1} '. Format (host, status))

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