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45 lines
1.1 KiB
Markdown
45 lines
1.1 KiB
Markdown
# TCP echo server
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## Concepts
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- Listening for TCP port connections with
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[Deno.listen](https://doc.deno.land/builtin/stable#Deno.listen).
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- Use [Deno.copy](https://doc.deno.land/builtin/stable#Deno.copy) to take
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inbound data and redirect it to be outbound data.
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## Example
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This is an example of a server which accepts connections on port 8080, and
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returns to the client anything it sends.
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```ts
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/**
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* echo_server.ts
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*/
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const listener = Deno.listen({ port: 8080 });
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console.log("listening on 0.0.0.0:8080");
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for await (const conn of listener) {
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Deno.copy(conn, conn);
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}
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```
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Run with:
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```shell
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deno run --allow-net echo_server.ts
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```
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To test it, try sending data to it with
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[netcat](https://en.wikipedia.org/wiki/Netcat) (Linux/MacOS only). Below
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`'hello world'` is sent over the connection, which is then echoed back to the
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user:
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```shell
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$ nc localhost 8080
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hello world
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hello world
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```
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Like the [cat.ts example](./unix_cat.md), the `copy()` function here also does
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not make unnecessary memory copies. It receives a packet from the kernel and
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sends back, without further complexity.
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