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<TITLE>libsnmp-python: I get errors when using snmpgetnext or snmpwalk</TITLE>
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<P><FONT SIZE=2 FACE="Arial CE">Package: libsnmp-python</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Version: 5.4.2.1~dfsg-5+b1</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Severity: important</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Tags: squeeze</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">When using the python bindings for net-snmp, I get errors when using snmpgetnext or snmpwalk. All installed software is from standard Debian distribution</FONT></P>
<P><FONT SIZE=2 FACE="Arial CE">Detailed description:</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">I try to communicate with a network device via SNMP. I send the same commands using command line tools and then using Python module libsnmp. The system is configured in such a way that I don't need to enter information about MIBS and paths on the commandline.</FONT></P>
<P><FONT SIZE=2 FACE="Arial CE">The following command are taken form tutorial on </FONT><A HREF="http://www.net-snmp.org/wiki/index.php/TUT:snmpwalk"><U><FONT COLOR="#0000FF" SIZE=2 FACE="Arial CE">http://www.net-snmp.org/wiki/index.php/TUT:snmpwalk</FONT></U></A>
</P>
<P><FONT SIZE=2 FACE="Arial CE">##############################################</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">On Debian Squeeze:</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">==============================================</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Scenario 1: command line</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">~$ snmpget --version</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">NET-SNMP version: 5.4.2.1</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">~$ ip="192.168.52.221:160"</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">~$ com="public"</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">~$ snmpwalk -v 2c -c $com $ip sysDescr</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">RFC1213-MIB::sysDescr.0 = STRING: "Some description"</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">~$ snmpgetnext -v 2c -c $com $ip sysDescr</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">RFC1213-MIB::sysDescr.0 = STRING: "Some description"</FONT>
</P>
<BR>
<BR>
<P><FONT SIZE=2 FACE="Arial CE">Everything works as expected</FONT>
</P>
<BR>
<P><FONT SIZE=2 FACE="Arial CE">==============================================</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Scenario 2: libsnmp in Python, snmpgetnext</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">~$ python</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Python 2.5.5 (r255:77872, Apr 21 2010, 08:44:16) </FONT>
<BR><FONT SIZE=2 FACE="Arial CE">[GCC 4.4.3] on linux2</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Type "help", "copyright", "credits" or "license" for more information.</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> import netsnmp</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> oid = netsnmp.Varbind('sysDescr')</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> ip="192.168.52.221:160"</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> com="tester"</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> </FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> res = netsnmp.snmpwalk(oid, Version = 2, DestHost = ip, Community = com); res</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">error: walk: unknown python error (varlist)>>> </FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> res = netsnmp.snmpwalk(oid, Version = 2, DestHost = ip, Community = com); res</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Traceback (most recent call last):</FONT>
<BR><FONT SIZE=2 FACE="Arial CE"> File "<stdin>", line 1, in <module></FONT>
<BR><FONT SIZE=2 FACE="Arial CE">TypeError: expected string or Unicode object, NoneType found</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> </FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">An error occurs. Notice that I get a different error after the second try.</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">==============================================</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Scenario 3: libsnmp in Python, snmpwalk</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">~$ python</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Python 2.5.5 (r255:77872, Apr 21 2010, 08:44:16) </FONT>
<BR><FONT SIZE=2 FACE="Arial CE">[GCC 4.4.3] on linux2</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Type "help", "copyright", "credits" or "license" for more information.</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> </FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> import netsnmp</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> oid = netsnmp.Varbind('sysDescr')</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> ip="192.168.52.221:160"</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> com="tester"</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> res = netsnmp.snmpgetnext(oid, Version = 2, DestHost = ip, Community = com); res</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">error: get: unknown python error>>> </FONT>
<BR><FONT SIZE=2 FACE="Arial CE">>>> res = netsnmp.snmpgetnext(oid, Version = 2, DestHost = ip, Community = com); res</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Traceback (most recent call last):</FONT>
<BR><FONT SIZE=2 FACE="Arial CE"> File "<stdin>", line 1, in <module></FONT>
<BR><FONT SIZE=2 FACE="Arial CE">TypeError: expected string or Unicode object, NoneType found</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">The same problem as in Scenario 2</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">##############################################</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">On Debian Lenny</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">It works as expected (the same results as from commandline). Below is a version of SNMP and python</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">~$ snmpget --version</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">NET-SNMP version: 5.4.1</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">~$ python</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Python 2.5.2 (r252:60911, Jan 24 2010, 14:53:14) </FONT>
<BR><FONT SIZE=2 FACE="Arial CE">[GCC 4.3.2] on linux2</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Type "help", "copyright", "credits" or "license" for more information.</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">-- System Information:</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Debian Release: squeeze/sid</FONT>
<BR><FONT SIZE=2 FACE="Arial CE"> APT prefers testing</FONT>
<BR><FONT SIZE=2 FACE="Arial CE"> APT policy: (500, 'testing')</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Architecture: i386 (i686)</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">Kernel: Linux 2.6.32-trunk-686 (SMP w/1 CPU core)</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8)</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">Shell: /bin/sh linked to /bin/dash</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">Versions of packages libsnmp-python depends on:</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">ii libc6 2.10.2-6 Embedded GNU C Library: Shared lib</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">ii libsnmp15 5.4.2.1~dfsg-5+b1 SNMP (Simple Network Management Pr</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">ii python 2.5.4-9 An interactive high-level object-o</FONT>
<BR><FONT SIZE=2 FACE="Arial CE">ii python-central 0.6.14+nmu2 register and build utility for Pyt</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">libsnmp-python recommends no packages.</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">libsnmp-python suggests no packages.</FONT>
</P>
<P><FONT SIZE=2 FACE="Arial CE">-- no debconf information</FONT>
</P>
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