That won't work.
Unless the client sent a message to the server first (which has portforwarding on that udp port) you will not be able to send the client anything as TCP and UDP are not handled as one by the NAT.
-> client has to contact server first if server wants to answer and it has to be on the same protocol as long as the incomming udp port has no static forwarding (or triggered one basing on the tcp port) to the desired system.
Unless the client sent a message to the server first (which has portforwarding on that udp port) you will not be able to send the client anything as TCP and UDP are not handled as one by the NAT.
-> client has to contact server first if server wants to answer and it has to be on the same protocol as long as the incomming udp port has no static forwarding (or triggered one basing on the tcp port) to the desired system.