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* vpnserver.c vpn server program via UDP  
* vpnclient.c vpn client program via UDP 
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To compile the compile: 
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$ make 


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To run the server: 
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$ sudo ./vpnserver


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To run the client: 
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First change the SERVER_IP in vpnclient.c to match with the server's ip.  
$ sudo ./vpnclient

Note: You also need to configure the TUN interfaces on both sides
and set up routings. See the lab description for instructions.