gosnmp.Connect() return not nil even with remote snmpd daemon stoped about gosnmp HOT 7 CLOSED

This is expected. Because UDP is a connectionless protocol, there's no actual connection created. The Connect() method simply creates and opens the socket. Until something is sent across it, you don't know that the remote host is there and responding.
Even if you were able to detect that the remote host is there on Connect(), it could go away by the time you sent something. And it could also come back again at any time.

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I'm overseas at the moment, can I
look it later?

On 15 June 2016 at 20:10, Toni Moreno [email protected] wrote:

Hi @soniah https://github.com/soniah . I'm building some improvements
in mi snmpcollector, I would like detect when snmp device is offline to try
do periodic re-connections.

When doing the first connection it returns non nil value , but my snmpd
daemon is stopped

https://github.com/toni-moreno/snmpcollector/blob/master/pkg/snmp.go#L172

After when trying to do a bulkwalk the client detects errors.

INFO[0000] First SNMP connection to host hostsnmpv3b stablished <--here first gosnmp.Connect()
INFO[0000] Filter not found for measurement:i linux_cpu
INFO[0000] Loading Indexed values in : linux_ports
FATA[0000] SNMP bulkwalk error Error reading from UDP: read udp 127.0.0.1:55412->127.0.0.1:161: read: connection refused

Can you review if I'm doing something wrong ?

Thank you very much

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yes of course! thank you !!

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@phemmer is correct. UDP is stateless, so unless you build your own 'connection' construct on top of it, all you get when you 'Connect()' is a listening socket where you can send data and where you can try and receive data.

What I suspect you would want to do is attempt to poll the device; if it returns an error or a value, then you can consider it online.

I'd suggest this issue is closed.

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Closed - see comments about UDP being stateless. Thank you @toni-moreno @phemmer @schotlandzegtja for your request and comments :-)

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Hi @phemmer and @soniah IMHO if we are working only with a connectionless protocol the gonsmp.Connect() is not a good API Method name, could be better something like gosnmp.PrepareProtocol()

When I did the first Connect() I expect the method can do something in the server side to give me an idea that server side is ok.

IMHO the documentation also give us an erroneous idea on what this method does.

https://godoc.org/github.com/soniah/gosnmp#GoSNMP.Connect

What do you think about?

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Thank you Toni. I've updated the documentation:

Connect creates and opens a socket. Because UDP is a connectionless protocol, you won't know if the remote host is responding until you send packets. And if the host is regularly disappearing and reappearing, you won't know if you've only done a Connect().

For historical reasons (ie this is part of the public API), the method won't be renamed.

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