Networking :: Unable To Route Traffic Based On Packet Content

My linux machine is connected to the outside internet, and I have a minecraft server running on an internal machine (192.168.1.201). Right now, I am forwarding port 80 on the linux machine to 192.168.1.30, which is working.

iptables -t nat -I PREROUTING -i eth0 -d 192.168.1.30 -j DNAT --to-destination 192.168.1.201
iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
iptables -A PREROUTING -t nat -i eth0 -p tcp --dport 80 -m state --state NEW,ESTABLISHED,RELATED -j DNAT --to 192.168.1.201

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I want to filter out the GET/POST requests and forward them to port 8080. I can't seem to get that working.

I've tried this:

iptables -A INPUT -d 192.168.1.30 -p tcp --dport 80 -m string --algo bm --string 'GET' -j REDIRECT --to-ports 8080