On this post http://pysnmp.sourceforge.net/examples/current/v1arch/manager/cmdgen/getnext-v1.html I was able to change the pdu on the fly for one device at a time, but I struggled to send a request to more the one device at the same time.
I tried doing the following:
transportDispatcher.registerTransport(
udp.domainName, udp.UdpSocketTransport().openClientMode()
)
transportDispatcher.sendMessage(
encoder.encode(reqMsg), udp.domainName, ('demo.snmplabs.com', 161)
)
transportDispatcher.jobStarted(1)
transportDispatcher.registerTransport(
udp.domainName, udp.UdpSocketTransport().openClientMode()
)
transportDispatcher.sendMessage(
encoder.encode(reqMsg), udp.domainName, ('192.168.0.49', 161)
)
transportDispatcher.jobStarted(1)
But I get the following error: "pysnmp.carrier.error.CarrierError: Transport (1, 3, 6, 1, 6, 1, 1) already registered".
So how do I change PDU on the fly and send a SNMP request to multiple devices on the same time?
Strictly speaking, you are not changing PDU on the fly, rather you are building different SNMP messages and sending them independently through the same network transport.
The problem with your code is that you are trying to register multiple UDP sockets under the same SNMP transport ID. You do not need that, as you could send UDP datagrams to multiple destinations through a single socket.
Therefore transport registration should only be performed once in your code:
# one-time initialization
transportDispatcher.registerTransport(
udp.domainName, udp.UdpSocketTransport().openClientMode()
)
# messaging
while True:
transportDispatcher.sendMessage(
encoder.encode(reqMsg), udp.domainName, ('demo.snmplabs.com', 161)
)
transportDispatcher.jobStarted(1)
...
Side note: DNS resolver is not asynchronous, make sure it works fast enough or use IP addresses for addressing your agents.
If you want multiple UDP sockets for some reason, use different SNMP transport IDs for them for both registration and use:
transportDispatcher.registerTransport(
udp.domainName + (1,), udp.UdpSocketTransport().openClientMode()
)
transportDispatcher.registerTransport(
udp.domainName + (2,), udp.UdpSocketTransport().openClientMode()
)
Related
I'm trying to send multiples packets to test a server , but i need to send different traffic pattern ( send IPv4,ICMP,Ipv6...) but i can't even specify one type when sending the streams
[EDIT-1]
CMD: ./build/MoonGen ./packetgen.lua -tx 0 -rx 1
packetgen.lua is the default script present in LYA folder of Moongen
I build a small SNMP v3 trap receiver in python with pysnmp. In our network, the snmp enigine id and the users/passwords are equal on different machines. So i need the snmp trap senders ip address to identify the sending machine.
How can i get the address, is there any function/method in pysnmp?
I think it is generally discouraged in SNMP to rely on peer address because of potential proxy/NAT/etc in-between. That probably explains why peer address information is not exposed in abstract SNMP APIs.
Do get hold of peer address in pysnmp you could use the observer feature:
# Callback function for receiving notifications
def cbFun(snmpEngine, stateReference, contextEngineId, contextName,
varBinds, cbCtx):
execContext = snmpEngine.observer.getExecutionContext(
'rfc3412.receiveMessage:request'
)
print('Notification from %s:%s' % execContext['transportAddress'])
Here is the complete example.
I am learning to sockets and found the word Data OR Record Boundaries in SOCK_SEQPACKET communication protocol? Can anyone explain in simple words what is Data boundary and how the SOCK_SEQPACKET is different from SOCK_STREAM & SOCK_DGRAM ?
This answer https://stackoverflow.com/a/9563694/1076479 has a good succinct explanation of message boundaries (a different name for "record boundaries").
Extending that answer to SOCK_SEQPACKET:
SOCK_STREAM provides reliable, sequenced communication of streams of data between two peers. It does not maintain message (record) boundaries, which means the application must manage its own boundaries on top of the stream provided.
SOCK_DGRAM provides unreliable transmission of datagrams. Datagrams are self-contained capsules and their boundaries are maintained. That means if you send a 20 byte buffer on peer A, peer B will receive a 20 byte message. However, they can be dropped, or received out of order, and it's up to the application to figure that out and handle it.
SOCK_SEQPACKET is a newer technology that is not yet widely used, but tries to marry the benefits of both of the above. That is, it provides reliable, sequenced communication that also transmits entire "datagrams" as a unit (and hence maintains message boundaries).
It's easiest to demonstrate the concept of message boundaries by showing what happens when they're neglected. Beginners often post client code like this here on SO (using python for convenience):
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.connect(('192.168.4.122', 9000))
s.send(b'FOO') # Send string 1
s.send(b'BAR') # Send string 2
reply = s.recv(128) # Receive reply
And server code similar to this:
lsock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
lsock.bind(('', 9000))
lsock.listen(5)
csock, caddr = lsock.accept()
string1 = csock.recv(128) # Receive first string
string2 = csock.recv(128) # Receive second string <== XXXXXXX
csock.send(b'Got your messages') # Send reply
They don't understand then why the server hangs on the second recv call, while the client is hung on its own recv call. That happens because both strings the client sent (may) get bundled together and received as a single unit in the first recv on the server side. That is, the message boundary between the two logical messages was not preserved, and so string1 will often contain both chunks run together: 'FOOBAR'
(Often there are other timing-related aspects to the code that influence when/whether that actually happens or not.)
I'm trying to re-write one of our old Servers using ZeroMQ, for now I have the following Server setup, (which works for Zmq requests):
using (var context = ZmqContext.Create())
using (var server = context.CreateSocket(SocketType.REP)) {
server.Bind("tcp://x.x.x.x:5705");
while (true) { ... }
This kind of setup works fine if I use the Zmq client library to connect context.CreateSocket(SocketType.REQ)
But unfortunately we've got a lot of legacy code that needs to connect to this server and the sockets are created using .net socket libs:
Socket = new Socket(ipAddress.AddressFamily, SocketType.Stream, ProtocolType.Tcp);
Socket.Connect(ipAddress, port);
Is there a way to write a ZeroMQ Server to accept these traditional .net socket connections?
You can achieve this using ZMQ_STREAM sockets.
Please note that since zeroMQ 4.x, the RAW router option has been deprecated for a new ZMQ_STREAM socket type, that works the same way as ROUTER + RAW.
It seems it is bound to evolve, though.
I recently tried ZMQ_STREAM sockets in version 4.0.1.
You can open one, use zmq_rcv until you receive the whole message (you have to check it is whole yourself), or zmq_msg_rcv to let ZeroMQ handle it. You will receive an identifier message part, just like the identifier you would find in ROUTER sockets, directly followed by one ONLY body part. There is no empty delimiter between them like there would be using a REQ Socket talking to a ROUTER Socket. So if you route them, be sure to add it yourself.
Beware though: if there is latency on the other end or if your message exceeds ZeroMQ ZMQ_STREAM buffers (mine are 8192 bytes long), your message can be interpreted by zeroMQ as a series of messages.
In that case, you will receive as many different ZeroMQ messages including both the identifier part and the body part, and it is your job to aggregate them, knowing that if several clients are talking to the STREAM socket, they might get mixed up. I personnally use a hash table using the binary identifier as a key, and delete the entry from the table when I know the message is complete and sent to the next node.
Sending through a ZMQ_STREAM with zmq_msg_send or zmq_send works fine as is.
You probably have to use zmq's RAW socket type (instead of REP) to connect with and read client data without zmq-specific framing.
HTTP Server in C (from Pieter's blog)
http://hintjens.com/blog:42
RAW Socket type info
https://github.com/hintjens/libzmq/commit/777c38ae32a5d1799b3275d38ff8d587c885dd55
Ok in order to broadcast, I have created a socket:
notifySock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);
And to send the hostname of my computer to all other computers connected to the same lan, I am using the send(Byte[] buffer) method:
notifySock.Send(hostBuffer);
hostBuffer contains the hostname of my computer.
However because I am using a 'datagram' socket-type do I need to format the data I need to send.
If possible please provide the code that I must put in between the two lines of code I have entered to create a socket and send the data.
For broadcast from a user application, UDP is typically used. You need to design a suitable protocol, i.e. a way to format the information you want to send into the UDP packet.
In your example you haven't specified who you are sending to. You need something like:
UdpClient notifySock = new UdpClient(endPoint);
notifySock.Send(buffer, buffer.Length, new IPEndPoint(IPAddress.Broadcast, 1234));
For the other hosts on your LAN to receive that they have to be listening on UDP port 1234.