pub fn new(forward_addr: Address, client_addr: ServerAddr, balancer: PingBalancer) -> Self {
        let context = ServiceContext::new();
        Self::with_context(Arc::new(context), forward_addr, client_addr, balancer)
    }
Create a new Tunnel server forwarding to `forward_addr`
crates/shadowsocks-service/src/local/tunnel/server.rs