DataoutputStream.close() Erro

public final InputStream post(final byte[] b, final String url) throws IOException {
    conn = (HttpConnection) Connector.open(url);
    conn.setRequestMethod(HttpConnection.POST);
    conn.setRequestProperty("User-Agent",
    "Profile/MIDP-1.0 Configuration/CLDC-1.0");   
    conn.setRequestProperty("Accept", "application/octet-stream");
    conn.setRequestProperty( "Connection", "close"); // optional. Remember the
    conn.setRequestProperty("Content-Length", Integer.toString(b.length));


    os = conn.openOutputStream();
    os.write(b);
    try{
        os.close();
    }
    catch(Exception io)
    {
        //ignore
    }



    int rc = conn.getResponseCode();

    if (rc != HttpConnection.HTTP_OK) {
        throw new IOException("Unexpected HTTP response: " + rc);
    }


return is;

}