I succcesfully created SNMP agent using snmp4j libraray
Here is the refrence code.
My query is how can i make this agent to run always to listen all incoming OIDs from manager.??
public synchronized void listen() throws IOException
{
TransportIpAddress address2= new UdpAddress(2069);
AbstractTransportMapping transport;
if (address2 instanceof TcpAddress)
{
transport = new DefaultTcpTransportMapping((TcpAddress) address2);
}
else
{
// transport = new DefaultUdpTransportMapping( (UdpAddress) address2);
transport = new DefaultUdpTransportMapping();
}
ThreadPool threadPool = ThreadPool.create("DispatcherPool", 10);
MessageDispatcher mtDispatcher = new MultiThreadedMessageDispatcher(threadPool, new MessageDispatcherImpl());
// add message processing models
mtDispatcher.addMessageProcessingModel(new MPv1());
mtDispatcher.addMessageProcessingModel(new MPv2c());
// add all security protocols
SecurityProtocols.getInstance().addDefaultProtocols();
SecurityProtocols.getInstance().addPrivacyProtocol(new Priv3DES());
//Create Target
CommunityTarget target = new CommunityTarget();
target.setCommunity( new OctetString("password"));
Snmp snmp = new Snmp(mtDispatcher, transport);
snmp.addCommandResponder(this);
transport.listen();
System.out.println("Listening on " + address);
try
{
this.wait();
}
catch (InterruptedException ex)
{
Thread.currentThread().interrupt();
}
}
Related
I have a Jersey server running locally, it exposes a SSE resource just like the examples here: https://jersey.github.io/documentation/latest/sse.html. I have a local webpack Angular app, that binds to the exposed GET endpoint and listens for data.
On the GET, I start up a thread to send notifications at regular intervals over 6-8 seconds. I don't see anything on the client UNTIL the EventOutput object is closed.
What am I doing wrong, and how can I fix this?
The server code WORKS with just a simple curl, i.e.:
curl http://localhost:8002/api/v1/notify
But on both Chrome and Safari the following code exhibits the behavior
Client (TypeScript):
this.evSource = new EventSource('http://localhost:8002/api/v1/notify');
this.evSource.addEventListener(
'event',
(x => console.log('we have ', x))
);
this.evSource.onmessage = (data => console.log(data));
this.evSource.onopen = (data => console.log(data));
this.evSource.onerror = (data => {
console.log(data);
this.evSource.close();
});
Server (Java):
// cache callback
public void eventCallback(Iterable<CacheEntryEvent<? extends Integer, ? extends Integer>> events) {
for (CacheEntryEvent<? extends Integer, ? extends Integer> x : events) {
LOGGER.info("{} Sending the following value: " + x.getValue(), Thread.currentThread().getId());
final OutboundEvent sseEvent = new OutboundEvent.Builder().name("event")
.data(Integer.class, x.getValue()).build();
this.broadcaster.broadcast(sseEvent);
}
}
#GET
#Produces(SseFeature.SERVER_SENT_EVENTS)
#ApiOperation(value = "Setup SSE pipeline", notes = "Sets up the notification pipeline for clients to access")
#ApiResponses(value = {
#ApiResponse(code = HttpURLConnection.HTTP_UNAUTHORIZED,
message = "Missing, bad or untrusted cookie"),
#ApiResponse(code = HttpURLConnection.HTTP_OK,
message = "Events streamed successfully")
})
#Timed
#ResponseMetered
public EventOutput registerNotificationEvents(
#HeaderParam(SseFeature.LAST_EVENT_ID_HEADER) String lastEventId,
#QueryParam(SseFeature.LAST_EVENT_ID_HEADER) String lastEventIdQuery) {
if (!Strings.isNullOrEmpty(lastEventId) || !Strings.isNullOrEmpty(lastEventIdQuery)) {
LOGGER.info("Found Last-Event-ID header: {}", !Strings.isNullOrEmpty(lastEventId) ? lastEventId : lastEventIdQuery );
}
LOGGER.info("{} Received request", Thread.currentThread().getId());
this.continuation = true;
final EventOutput output = new EventOutput();
broadcaster.add(output);
Random rand = new Random();
IntStream rndStream = IntStream.generate(() -> rand.nextInt(90));
List<Integer> lottery = rndStream.limit(15).boxed().collect(Collectors.toList());
IgniteCache<Integer, Integer> cache = this.ignite.cache(topic_name);
executorService.execute(() -> {
try {
lottery.forEach(value -> {
try {
TimeUnit.MILLISECONDS.sleep(500);
LOGGER.info("{} Sending the following value to Ignite: " + value + " : " + count++, Thread.currentThread().getId());
if (!cache.isClosed()) {
cache.put(1, value);
}
} catch (InterruptedException ex) {
ex.printStackTrace();
}
});
TimeUnit.MILLISECONDS.sleep(500);
continuation = false;
TimeUnit.MILLISECONDS.sleep(500);
if (!output.isClosed()) {
// THIS is where the client sees ALL the data broadcast
// in one shot
output.close();
}
} catch (InterruptedException ex) {
ex.printStackTrace();
} catch (IOException ex) {
ex.printStackTrace();
}
});
LOGGER.info("{} Completing request", Thread.currentThread().getId());
return output;
}
}
Looks like http://github.com/dropwizard/dropwizard/issues/1673 captures the problem. GZip default won't flush even if upper levels ask for it. Solution is something like
((AbstractServerFactory)configuration.getServerFactory()).getGzipFilterFactory().setSyncFlush(true);
will enable flushing to synchronize with GZip if disabling GZip all up is not an option
I have a cluster of rabbitmqs. And configure the spring.rabbitmq.address=xxx,yyy,cccc
Then I start two consumer clients. The question is that the clients only connect one node, there,s not connection to the other nodes. I trace the codes, and found that :
public Connection newConnection(ExecutorService executor, AddressResolver addressResolver, String clientProvidedName) throws IOException, TimeoutException {
if (this.metricsCollector == null) {
this.metricsCollector = new NoOpMetricsCollector();
}
FrameHandlerFactory fhFactory = this.createFrameHandlerFactory();
ConnectionParams params = this.params(executor);
if (clientProvidedName != null) {
Map<String, Object> properties = new
HashMap(params.getClientProperties());
properties.put("connection_name", clientProvidedName);
params.setClientProperties(properties);
}
if (this.isAutomaticRecoveryEnabled()) {
AutorecoveringConnection conn = new AutorecoveringConnection(params,
fhFactory, addressResolver, this.metricsCollector);
conn.init();
return conn;
} else {
List<Address> addrs = addressResolver.getAddresses();
Exception lastException = null;
Iterator var8 = addrs.iterator();
while(var8.hasNext()) {
Address addr = (Address)var8.next();
try {
**FrameHandler handler = fhFactory.create(addr);
AMQConnection conn = this.createConnection(params, handler, this.metricsCollector);
conn.start();
this.metricsCollector.newConnection(conn);
return conn;**
} catch (IOException var12) {
lastException = var12;
} catch (TimeoutException var13) {
lastException = var13;
}
}
if (lastException != null) {
if (lastException instanceof IOException) {
throw (IOException)lastException;
}
if (lastException instanceof TimeoutException) {
throw (TimeoutException)lastException;
}
}
throw new IOException("failed to connect");
}
}
We can see that it creates one connection then returned. But if I wanna the other consumer client can connect to the left nodes instead the same node, although both of the consumer clients have the same configuration:
spring:
rabbitmq:
username: aaaa
password: aaaa
virtual-host: /
addresses: xxxx:5672,yyy:5672,zzzzz:5672
listener:
simple:
concurrency: 4
max-concurrency: 4
prefetch: 4
What should I do ？ can someone give some suggestions?
The RabbitMQ team monitors this mailing list and only sometimes answers questions on StackOverflow.
Try rotating the list of addresses in each client's configuration:
First - xxxx:5672,yyy:5672,zzzzz:5672
Second - yyy:5672,zzzzz:5672,xxxx:5672
Third - zzzzz:5672,xxxx:5672,yyy:5672
I created MyListener which will start listening (using TcpListener) on his own thread upon creation. the TcpListener should handle multiple clients so i am running inside infinte while and handle each client in special task.
this is my code:
public class MyListener
{
public event EventHandler<MessageEventArgs> MessageReceived;
public MyListener()
{
var thread = new Thread(Listen);
thread.Start();
}
private void Listen()
{
TcpListener server = null;
try
{
server = new TcpListener(IPAddress.Any, 8977);
server.Start();
while (true)
{
var client = server.AcceptTcpClient();
Task.Run(() =>
{
try
{
var msg = GetMessageFromClient(client);
MessageReceived?.Invoke(this, new MessageEventArgs { Message = msg });
}
catch (Exception)
{
}
finally
{
client.Close();
}
});
}
}
catch (Exception)
{
}
finally
{
if (server != null)
server.Stop();
}
}
private string GetMessageFromClient(TcpClient client)
{
var bytes = new byte[client.ReceiveBufferSize];
var stream = client.GetStream();
var i = stream.Read(bytes, 0, bytes.Length);
var message = Encoding.UTF8.GetString(bytes, 0, i);
return message;
}
}
here are my questions:
how can i ensure that the task handle the client will use the client i pass to it when i start the task and not different client (becuase after the task start we return to the AcceptTcpClient method and may get new client)
in my example and with multiple clients handled by the same method ("GetMessageFromClient") do i need to put some kind of locking on this
method?
I am getting a crash course in delegates and event handlers and I have been following a tutorial on the subject and trying to plug in what I have learned into a socket server program I am creating.
I am trying to decouple my server from knowing about the AlertConnectionOpened class here:
namespace AlertConnectionOpened
{
//This is a subscriber class
public class AlertConnectionOpened
{
public void OnConnectionOpened(string message)
{
Console.WriteLine("Connection is opened");
}
}
}
So I am using a delegate in my server class to accomplish this.
namespace Server
{
public class RunServer
{
// State object for reading client data asynchronously
public class StateObject
{
// Client socket.
public Socket workSocket = null;
// Size of receive buffer.
public const int BufferSize = 1024;
// Receive buffer.
public byte[] buffer = new byte[BufferSize];
// Received data string.
public StringBuilder sb = new StringBuilder();
}
public class AsynchronousSocketListener
{
// Thread signal.
public ManualResetEvent allDone = new ManualResetEvent(false);
public AsynchronousSocketListener(int port)
{
}
//This defines the delegate
//Agreement between publisher and subscriber
//object, source of event or class publishing or sending data,
//second param is any additional data we need to send.
public delegate void ConnectionOpenEventHandler(string Message);
//Indicates something has happened and finished.
//Event defined here, based on delegate
public event ConnectionOpenEventHandler ConnectionOpened;
//Raise the Event, need a method to do this.
//Responsible for notifying subscribers
protected virtual void OnConnectionOpened()
{
if (ConnectionOpened != null)
ConnectionOpened("Connection Opened");
}
public void StartListening()
{
// Data buffer for incoming data.
byte[] bytes = new Byte[1024];
int port = 11000;
// Establish the local endpoint for the socket.
// The DNS name of the computer
// running the listener is "host.contoso.com".
IPHostEntry ipHostInfo = Dns.Resolve(Dns.GetHostName());
IPAddress ipAddress = ipHostInfo.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(ipAddress, port);
// Create a TCP/IP socket.
Socket listener = new Socket(AddressFamily.InterNetwork,
SocketType.Stream, ProtocolType.Tcp);
// Bind the socket to the local endpoint and listen for incoming connections.
try
{
listener.Bind(localEndPoint);
//backlog of how many clients to take in
listener.Listen(100);
while (true)
{
// Set the event to nonsignaled state.
allDone.Reset();
// Start an asynchronous socket to listen for connections.
Console.WriteLine("Waiting for a connection...");
listener.BeginAccept(
new AsyncCallback(AcceptCallback),
listener);
// Wait until a connection is made before continuing.
allDone.WaitOne();
OnConnectionOpened();
}
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
Console.WriteLine("\nPress ENTER to continue...");
Console.Read();
}
public void AcceptCallback(IAsyncResult ar)
{
// Signal the main thread to continue.
allDone.Set();
// Get the socket that handles the client request.
Socket listener = (Socket)ar.AsyncState;
Socket handler = listener.EndAccept(ar);
// Create the state object.
StateObject state = new StateObject();
state.workSocket = handler;
handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(ReadCallback), state);
}
public void ReadCallback(IAsyncResult ar)
{
String content = String.Empty;
// Retrieve the state object and the handler socket
// from the asynchronous state object.
StateObject state = (StateObject)ar.AsyncState;
Socket handler = state.workSocket;
// Read data from the client socket.
int bytesRead = handler.EndReceive(ar);
if (bytesRead > 0)
{
// There might be more data, so store the data received so far.
state.sb.Append(Encoding.ASCII.GetString(
state.buffer, 0, bytesRead));
// Check for end-of-file tag. If it is not there, read
// more data.
content = state.sb.ToString();
if (content.IndexOf("<EOF>") > -1)
{
// All the data has been read from the
// client. Display it on the console.
Console.WriteLine("Read {0} bytes from socket. \n Data : {1}",
content.Length, content);
Random rand = new Random();
content = rand.ToString();
// Echo the data back to the client.
Send(handler, content);
}
else {
// Not all data received. Get more.
handler.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0,
new AsyncCallback(ReadCallback), state);
}
}
}
public void Send(Socket handler, String data)
{
// Convert the string data to byte data using ASCII encoding.
byte[] byteData = Encoding.ASCII.GetBytes(data);
// Begin sending the data to the remote device.
handler.BeginSend(byteData, 0, byteData.Length, 0,
new AsyncCallback(SendCallback), handler);
}
public void SendCallback(IAsyncResult ar)
{
try
{
// Retrieve the socket from the state object.
Socket handler = (Socket)ar.AsyncState;
// Complete sending the data to the remote device.
int bytesSent = handler.EndSend(ar);
Console.WriteLine("Sent {0} bytes to client.", bytesSent);
handler.Shutdown(SocketShutdown.Both);
handler.Close();
}
catch (Exception e)
{
Console.WriteLine(e.ToString());
}
}
public static int Main(String[] args)
{
AsynchronousSocketListener a = new AsynchronousSocketListener(0);
a.StartListening();
return 0;
}
}
}
}
Here is also my main program:
namespace AppStart
{
class ServerStart
{
static void Main(string[] args)
{
RunServer.AsynchronousSocketListener svr1 = new RunServer.AsynchronousSocketListener(11000);//publisher
//Correct the port number so a second server can open
RunServer.AsynchronousSocketListener svr2 = new RunServer.AsynchronousSocketListener(350);
svr1.StartListening();//publisher
//This creates the subscriber
var alertConnectionOpened = new AlertConnectionOpened.AlertConnectionOpened();//subsciber
//make publisher register the handler for the event.
svr1.ConnectionOpened += alertConnectionOpened.OnConnectionOpened; //POinter to method
svr2.StartListening();
Console.ReadLine();
}
}
}
From the little I understand of this my call to OnConnectionOpened();, should be showing the message that there is now a connection, but it isn't.
I've been doing some very basic SNMP4J programming. All I want to do is send a simple "get" request but so far my responses have been null. I opened up wireshark and found that in the under Simple Network Management Protocol, my msgUserName is blank and I need that to be populated.
I thought I had set it using the following code:
Snmp snmp = new Snmp(transport);
USM usm = new USM(SecurityProtocols.getInstance(), new OctetString(MPv3.createLocalEngineID()), 0);
SecurityModels.getInstance().addSecurityModel(usm);
transport.listen();
UsmUser user = new UsmUser(new OctetString("SNMPManager"), AuthSHA.ID,new OctetString("password"),null,null);
// add user to the USM
snmp.getUSM().addUser(user.getSecurityName(), user);
Am I going about it the wrong way? If not, how do I set the msgUserName as seen in my wireshark dump of the get-request? I'm very new to SNMP, so I'm essentially running off examples.
This is a working snmpset you can write snmp get same way.Snmp4j v2 and v3 not using same api classes.
private void snmpSetV3(VariableBinding[] bindings) throws TimeOutException, OperationFailed {
Snmp snmp = null;
try {
PDU pdu = new ScopedPDU();
USM usm = new USM(SecurityProtocols.getInstance(), new OctetString(MPv3.createLocalEngineID()), 0);
SecurityModels.getInstance().addSecurityModel(usm);
snmp = new Snmp(new DefaultUdpTransportMapping());
snmp.getUSM().addUser(new OctetString(Username), new UsmUser(new OctetString(Username), AuthMD5.ID, new OctetString(Password), AuthMD5.ID, null));
ScopedPDU scopedPDU = (ScopedPDU) pdu;
scopedPDU.setType(PDU.SET);
scopedPDU.addAll(bindings);
UserTarget target = new UserTarget();
target.setAddress(new UdpAddress(IPAddress + "/" + Port));
target.setVersion(version); //SnmpConstants.version3
target.setRetries(retries);
target.setTimeout(timeout);
target.setSecurityLevel(securityLevel); //SecurityLevel.AUTH_NOPRIV
target.setSecurityName(new OctetString(Username));
snmp.listen();
ResponseEvent response = snmp.send(pdu, target);
if (response.getResponse() != null) {
PDU responsePDU = response.getResponse();
if (responsePDU != null) {
if (responsePDU.getErrorStatus() == PDU.noError) {
return;
}
throw new OperationFailed("Error: Request Failed, "
+ "Error Status = " + responsePDU.getErrorStatus()
+ ", Error Index = " + responsePDU.getErrorIndex()
+ ", Error Status Text = " + responsePDU.getErrorStatusText());
}
}
throw new TimeOutException("Error: Agent Timeout... ");
} catch (IOException e) {
throw new OperationFailed(e.getMessage(), e);
} finally {
if (snmp != null) {
try {
snmp.close();
} catch (IOException ex) {
_logger.error(ex.getMessage(), ex);
}
}
}
}