---
title: SSE Streaming
sidebar:
  icon: radio-tower
description: Stream values from the server as they happen, and read them with the same client call.
---

Return an `async function*` from `.run()`. The [HTTP](/tacho/transport/http) client is the same call; `for await` the result. [WebSocket](/tacho/transport/websocket) and batch reject streams. Notifications to a stream procedure are 204 and do not start the generator.

```ts twoslash
import { tacho } from "tacho";
import { z } from "zod";

const rpc = tacho();

export const router = rpc({
  ticks: rpc.input(z.object({ n: z.number() })).run(async function* ({
    input,
  }) {
    for (let i = 0; i < input.n; i++) yield { i };
  }),
});
```

```ts twoslash
import { createClient } from "tacho/client/http";
import { tacho } from "tacho";
import { z } from "zod";

const rpc = tacho();
const router = rpc({
  ticks: rpc.input(z.object({ n: z.number() })).run(async function* ({
    input,
  }) {
    for (let i = 0; i < input.n; i++) yield { i };
  }),
});
const client = createClient<typeof router>({
  url: "http://localhost:3000",
});
// ---cut---
const ticks = await client.ticks({ n: 3 });
for await (const t of ticks) console.log(t.i);
await ticks.return();
```

Pass `{ signal }` as the second argument to abort the fetch. `await ticks.return()` also cancels.

```ts twoslash
import { createClient } from "tacho/client/http";
import { tacho } from "tacho";
import { z } from "zod";

const rpc = tacho();
const router = rpc({
  ticks: rpc.input(z.object({ n: z.number() })).run(async function* ({
    input,
  }) {
    for (let i = 0; i < input.n; i++) yield { i };
  }),
});
const client = createClient<typeof router>({
  url: "http://localhost:3000",
});
// ---cut---
const ac = new AbortController();
const ticks = await client.ticks({ n: 3 }, { signal: ac.signal });
ac.abort();
```

Wire: each `yield` is `data: { jsonrpc, id, result }`. Handler `return` is `event: done`. Throw is `event: error`.