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// Copyright (c) 2022-2023 Cloudflare, Inc.
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// Licensed under the Apache 2.0 license found in the LICENSE file or at:
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//     https://opensource.org/licenses/Apache-2.0
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// This is an ESM module implementing a simple Gopher client. Gopher is an old alternative to HTTP,
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// it is also a simple protocol which makes it ideal for demoing TCP sockets in workerd.
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//
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// This module implements both direct and proxied TCP connections. In order to make use of the
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// proxy you'll need to have an HTTP proxy running on port 1234 (this can be changed in config.capnp).
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//
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// Example usage once you have workerd running:
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//
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// - curl localhost:8080/ # Retrieve the main segment in gopher.floodgap.com.
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// - curl localhost:8080/gstats # Retrieve the "gstats" segment.
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// - curl localhost:8080/gstats?use_proxy=1 # Retrieve the "gstats" segment using the configured proxy.
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import { connect } from 'cloudflare:sockets';
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export default {
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  async fetch(req, env) {
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    const gopherAddr = "gopher.floodgap.com:70";
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    const url = new URL(req.url);
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    const useProxy = url.searchParams.has("use_proxy");
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    try {
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      const socket = useProxy ? env.proxy.connect(gopherAddr) : connect(gopherAddr);
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      // Write data to the socket. Specifically the "selector" followed by CR+LF.
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      const writer = socket.writable.getWriter()
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      const encoder = new TextEncoder();
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      const encoded = encoder.encode(url.pathname + "\r\n");
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      await writer.write(encoded);
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      // The Gopher server should now return a response to us and close the connection.
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      // So start reading from the socket.
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      const decoder = new TextDecoder();
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      let gopherResponse = "";
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      for await (const chunk of socket.readable) {
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        gopherResponse += decoder.decode(chunk, { stream: true });
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      }
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      gopherResponse += decoder.decode();
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      console.log("Read ", gopherResponse.length, " from Gopher server");
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      return new Response(gopherResponse, { headers: { "Content-Type": "text/plain" } });
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    } catch (error) {
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      return new Response("Socket connection failed: " + error, { status: 500 });
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    }
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  }
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};