I want to upload a byte stream with ktor-client. The body is set to a

ByteReadChannel

, but then the

Content-Length

-header is not set. Setting it manually throws:

Header(s) [Content-Length] are controlled by the engine and cannot be set explicitly
io.ktor.http.UnsafeHeaderException: Header(s) [Content-Length] are controlled by the engine and cannot be set explicitly

You can set

Content-Length

header by overriding

contentLength

property of an object of

OutgoingContent.ReadChannelContent

class. Here is an example:

val client = HttpClient(Apache)

val channel = ByteChannel()
channel.writeStringUtf8("hello")
channel.close()

val r = <http://client.post|client.post><String>("<https://httpbin.org/post>") {
    body = object : OutgoingContent.ReadChannelContent() {
        override val contentLength: Long
            get() = 5

        override fun readFrom(): ByteReadChannel {
            return channel
        }
    }
}

println(r)

Thank you very much. Would be cool, when this were in the Docs :)