Hi I am trying to use C (not python) for RTDE for a UR10e.  Can someone help me figure out how to pack the initial message, which I think should be 'v' for RTDE_GET_URCONTROL_VERSION.  It says two bytes for the package size and 1 byte for the package type.  I can open and connect thru the port but need help getting started with the basic header info in the first message I need to send.  

Can someone break this down for me?  Is this 
sendmsg[0]=8
sendmsg[1]=0
 sendmsg[2]='v'   

 for the header info or am I way off base?  

Here is how we did it in nodejs originally, we run new code now but this worked for a long time

_sendall(cmd, payload = '', callback) {
    let size = 3; //Header is always 3 bytes long, 2 bytes for the size, 1 byte for the command
    if (payload.length > 0) size += payload.length;
    let buf = new Buffer(size);
    buf.writeUInt16BE(size, 0);        // write the size at index 0
    buf.writeInt8(cmd, 2);             // write the command at index 2
    buf.write(payload.toString(), 3);  // write the payload starting at index 3 
    this.sock.write(buf, 'binary', err =>{
more code here but nothing pertinent to the discussion

Thanks, again for the help.  Am I not able to keep connections open to the dashboard (29999), a socket (50000) and another port (30002) at the same time as RTDE (30004)?  

So far I can send the command out but get no response to RTDE_REQUEST_PROTOCOL_VERSION which is the first command I try to send.  All the other ports are okay and are receiving data with their respective handles.