We have an API (Spring Boot) for file uploads. If file exists it returns 409.

But js client doesn't read this response and fails with error "net::ERR_CONNECTION_ABORTED".

From wireshark dump I see that the backend sends the response and then closes the connection:

I think the problem is that js client doesn't read the response as soon as it available. However, Postman is able to read the response correctly.

Is it possible to implement Postman's behavior in javascript? I've tried to read response stream with Fetch API, but no luck.

Sample client code:

function uploadFile() {
try {
    console.log("Start file upload");

    const selectedFiles = document.getElementById('input').files;
    if (selectedFiles.length == 0) {
        alert("No file selected");
        return;
    }

    const file = selectedFiles[0];

    return fetch("http://localhost:9091/api/v1/storage/upload?fileId=/upload-test/test.mp4", {
        method: 'PUT',
        body: file,
        headers: {
            'Content-Type': 'application/octet-stream'
        },
    })
        .then(response => {
            console.log("Processing response");

            const reader = response.body.pipeThrough(new TextDecoderStream()).getReader();

            return pump();

            function pump() {
                return reader.read().then(({ value, done }) => {
                    if (done) {
                        console.log("Finished stream reading");
                        return;
                    }

                    console.log(value);
                    return pump();
                });
            }
        })
        .catch((err) => console.error("error:", err));
} catch (error) {
    console.log(error);
}

}