Hi Ros people! My name is Santiago, i'm just beginning in robot-world, and i'm making a client from Pharo smalltalk. My first goal is make work the turtle simulator from XMLRPC.

So i have several questions, but right now i have two most important:

Considering a remote client (without direct access to server):

- How can i get the message definition related to a topic? Can i ask to the topic? Does the topic answer me in the error text something about the type?

- Is any definition of a common TCPROS package to take as example of topic usage?

In this case, i'd spend a lot of time today trying to send messages to the turtle throgh the velocity topic without any response (no movement, no error, no feedback at all) and i tried with the logs, but without any useful data.

The process i'm following is:

execute roscore
execute turtle node

then, from the client

register as publisher in Velocity topic

with the IP:PORT recived connect to the node with a TCP/ip connection
sending a message with:

header
        type: master getTopicTypeRelated:/turtle1/command_velocity; #here i get the topicType from getTopicTypes
        topic: /turtle1/command_velocity;
        latching: false;
        callerId: anArbitraryId;
        messageDefinition: 'float32 linear
float32 angular';
        md5Sum:'9d5c2dcd348ac8f76ce2a4307bd63a13'.

in the body of the request i tried with float numbers (2.0 0.0) for example.

All this data in binary.

I browse a lot of roscpp, rospy and rosjava trying to find how them create and serialize the data, but i dont find meaningful differences. Maybe i'm missing steps?

Thank you very much!

Santiago.