Real TCP from Java, via the relay

Browsers can't open raw TCP, so Java sockets are tunneled over a WebSocket to a local relay. Start it first: node wasm-jvm/framework/net/tcp-relay.cjs 8114, then set the relay URL below and press Fetch. Without a running relay the connection times out. (On the public HTTPS site a ws://localhost relay is blocked as mixed content — run this page locally over http for networking.)