Set custom headers to websocket request (ktor)

Question

I'm establishing a websocket connection from the client like this:

val client = HttpClient(CIO).config {
    install(WebSockets)
}

client.webSocket(
        method = HttpMethod.Get,
        host = "127.0.0.1",
        port = 8080,
        path = "/api") {

    // Send and receive messages
}

What I would like to do is add http headers to this request.

Ktor has a pretty length documentation, but despite this I am not able to locate how to do this.

Answer 1

Found out the answer after all:

client.webSocket(
        method = HttpMethod.Get,
        host = "127.0.0.1",
        port = 8080,
        path = "/api",
        request = {
            header("my_header", "my_header_value")
        }
) {
    // more

How to find this? From the signature of webSocket:

suspend fun HttpClient.webSocket(
        method: HttpMethod = HttpMethod.Get,
        host: String = "localhost",
        port: Int = DEFAULT_PORT,
        path: String = "/",
        request: HttpRequestBuilder.() -> Unit = {},
        block: suspend DefaultClientWebSocketSession.() -> Unit
): Unit

Here HttpRequestBuilder sounds like something that can customize requests (and indeed there is some documentation on that).

The signature means request should be a scoped closure where this will be HttpRequestBuilder.

This closure can then set headers or change other things. There is, for example, HttpRequestBuilder.header.