This is a small tutorial explaining the use of STOMP 1.2 using telnet ## Setup This tutorial is based on ActiveMQ 5.10. You can download a standalone version http://activemq.apache.org/activemq-5100-release.html. The stomp connector is enabled out-of-the-box. Should you however be using a different version (e.g, Fuse or Karaf based) then ensure the following connector is enabled in the conf/activemq.xml configuration file ```xml … … ``` Start the activemq broker (we are starting the broker in the foreground , which is easy during testing and development) ```shell $ cd apache-activemq-5.10.0 $ bin/activemq console ``` The tutorial below uses the hawtio console. When using activemq in standalone mode it is best you use the chrome plugin to connect to your broker: There is an excellent blog entry explaining how to setup hawtio for activemq : http://sensatic.net/activemq/activemq-and-hawtio.html ## Publish messages using STOMP ### Connect ```shell telnet telnet> open localhost 61613 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. ``` Some information on the protocol (from wikipedia):

Communication between client and server is through a "frame" consisting of a number of lines. The first line contains the command, followed by headers in the form : (one per line), followed by a blank line and then the body content, ending in a null character. Communication between server and client is through a MESSAGE, RECEIPT or ERROR frame with a similar format of headers and body content.

*Note*: The null character null character `^@` can be send to a linux terminal using `ctrl+@` (don't forget to use the shift) In the hawtio console you should be able to see the connection (`remoteAddress` child under `clientConnectors>stomp`) ### Next start a session The frame below initiates the session The `accept-version` and `host` headers are mandatory for STOMP 1.2 clients. ```shell CONNECT accept-version:1.2 host:localhost login:admin passcode:admin ^@ CONNECTED heart-beat:0,0 session:ID:hp-8570w-56234-1388604777495-2:1 server:ActiveMQ/5.10.0 version:1.2 ``` The hawtio console will now also show the client session Now that we have a session, we can use the following client frames - `SEND` - sends a message to a destination - `SUBSCRIBE` - subscribe to a destination - `UNSUBSCRIBE` - unsubscribe from a destination - `BEGIN` - starts a transaction - `COMMIT` - commits the transaction - `ABORT` - rollback the transaction - `ACK` - acknowledge of a message - `NACK` - tell server we did not consume the message - `DISCONNECT` - disconnect (always use the `receipt` header) The server will respond with one of the following frames - `MESSAGE` - message received by a subscriber - `RECEIPT` - a response indicating successful receipt of the frame sent by the client - `ERROR` - indicates something went wrong ### Send a message Below is an example SEND frame. It uses the Header receipt. This makes it easier to see the successful reception of the frame. The example send command below also has the recommended content-type header (note the) ```shell SEND destination:SomeQueue content-type:text/plain receipt:123 hello^@ RECEIPT receipt-id:123 ``` Consult the hawtio console and observe the message has been delivered ### disconnect The frame below disconnects from the server ```shell DISCONNECT receipt:789 ^@ RECEIPT receipt-id: Connection closed by foreign host. ``` ## Consume message using STOMP Start a telnet a new telnet session and connect to the broker as before. ### Subscribe to a destination The frame below subscribes to the `SomeQueue` destination. You need to pass the id header as we could have multiple open subscriptions in one session (this `id` is now indicated on each message which we receive) ```shell SUBSCRIBE id:0 destination:SomeQueue ack:client ^@ ``` You will immediately receive messages which were already on the queue. If you would go into hawtio and send a message, you will also receive that message instantly in the telnet STOMP session. We are using `client` acknowledgement (http://stomp.github.io/stomp-specification-1.2.html#SUBSCRIBE_ack_Header), other options are `client` and `client-individual`. Using `client` acknowledgement allows us to explicitly send `ACK` or `NACK` frames to indicate whether we want to acknowledge the receipt of the dispatched messages . Make sure you look at the hawtio console and notice how messages are dispatched but not yet dequeued. ### Acknowledge messages A received MESSAGE frame might look like: ```shell MESSAGE ack:ID\chp-8570w-60528-1388615318930-10\c1 message-id:ID\chp-8570w-60528-1388615318930-6\c1\c1\c1\c1 destination:/queue/SomeQueue timestamp:1388615697080 expires:0 subscription:0 persistent:true priority:0 hello ``` Notice the inclusion of the `ack` header. This header is used for the acknowledgement and is sent when using `client` and `client-individual` acknowledgement modes. To acknowledge all the received messages use the following frame ```shell ACK id:ID\chp-8570w-60528-1388615318930-10\c1 subscription:0 ^@ ``` This ACK frame is a cumulative acknowledgment, meaning all received messages are acknowledged. This is also standard behaviour when using Java JMS. Using an acknowledge mode of `client-individual` allows you to acknowledge individual messages. Also note you have to pass the `subscription` header. This is because acknowledgement id's could be equal between multiple subscriptions in a single session. GO ahead an notice the changes to the queue using the hawtio console. ### Unsubscribe To unsubscribe you just send a UNSUBSCRIBE frame containing the subscription value ```shell UNSUBSCRIBE id:0 receipt: ^@ ``` You can now disconnect as before.

STOMP 1.2 / ActiveMQ using Telnet

STOMP 1.2 / ActiveMQ using Telnet

Course Suggestions