I need to send very long programs to the robot to work with an extruder like 3dprinter, I connected it with the ethernet cable and when I send the program the robot doesn't start, as if it does not have enough memory, there is a way to send the code line by line?

Something that can be done could look like this:

you create a loop which run until you receive an end signal
  if the end signal is false
    first you wait that the position you receive is different from 0 and different from the previous
    reset a signal that say the trajectory is done
    you memorize this new point in a variable
    you do a move trajectory to this new point
    you send a signal that the trajectory is done


You could use others variables to decide which kind of move you want to do and for example get different speed.
This would give you a short program with everything done from the Ethernet. But it's just an idea, I've never tested it.

It depends on the robot you use. A lot of robots allow to include sub programs into a main one. This way the sub programs are in memory only when they are in use. It could be a solution.

Another approach would be to use socket connection and do most of the computation on a remote computer. Your robot program would be only a simple loop that ask the remote computer for the next waypoint and then move the robot there.

What kind of robot are you looking to use?  That will shape the answer depending on the capabilities of the different brands.

sorry... the robot is UR10

You could set up a server to actually send the script commands to the robot one at a time over port 30003.  YOu would need to have a way to monitor the position of the robot relative to the end position you sent so that you know each position is complete before sending the next one.  Or another way is you can send the commands as servoj moves and then you just need to keep sending them at the right frequency (125 Hz) so that you get smooth motion. 

I think the issue you might see trying to have a Polyscope program asking for and executing waypoints is it will possibly not have smooth motion which would affect your print quality.