Having trouble with poem gRPC server. When I'am trying to mock a nacos grpc server, I cannot establish http2 connection properly

[4t145]

1. client send Magic, SETTINGS[0], WINDOW_UPDATE[0]
2. server responde with tcp payload 15 03 03 00 02 02 32
   
3. but client expect an SETTINGS frame, so it send a GOAWAY[0], connection closed.

I noticed that 0x0303 looks like TLS version number TLS 1.2
When I'm using postman or grpcurl to test my grpc interface, all the things seems ok.

Is there any configuration I have missed?

update:
Response message looks like a tls handshake message ServerHello. So when client send a http/2 request, server was trying to establish a tls connection, and client see it as an error and terminate the connection. But how can I solve it?

update2:
it turns out java client send request in plaintext, so when server want to establish tls connection, it goes wrong.
tcpdumpfile.zip