mirror of
https://github.com/denoland/deno.git
synced 2024-11-01 09:24:20 -04:00
41 lines
1.2 KiB
Markdown
41 lines
1.2 KiB
Markdown
## TCP echo server
|
|
|
|
This is an example of a server which accepts connections on port 8080, and
|
|
returns to the client anything it sends.
|
|
|
|
```ts
|
|
const listener = Deno.listen({ port: 8080 });
|
|
console.log("listening on 0.0.0.0:8080");
|
|
for await (const conn of listener) {
|
|
Deno.copy(conn, conn);
|
|
}
|
|
```
|
|
|
|
When this program is started, it throws PermissionDenied error.
|
|
|
|
```shell
|
|
$ deno run https://deno.land/std@$STD_VERSION/examples/echo_server.ts
|
|
error: Uncaught PermissionDenied: network access to "0.0.0.0:8080", run again with the --allow-net flag
|
|
► $deno$/dispatch_json.ts:40:11
|
|
at DenoError ($deno$/errors.ts:20:5)
|
|
...
|
|
```
|
|
|
|
For security reasons, Deno does not allow programs to access the network without
|
|
explicit permission. To allow accessing the network, use a command-line flag:
|
|
|
|
```shell
|
|
deno run --allow-net https://deno.land/std@$STD_VERSION/examples/echo_server.ts
|
|
```
|
|
|
|
To test it, try sending data to it with netcat:
|
|
|
|
```shell
|
|
$ nc localhost 8080
|
|
hello world
|
|
hello world
|
|
```
|
|
|
|
Like the `cat.ts` example, the `copy()` function here also does not make
|
|
unnecessary memory copies. It receives a packet from the kernel and sends back,
|
|
without further complexity.
|