HttpURLConnection のデモ。

gistfile1.as

let line        : string;
let url         : URL               = new URL( "http://localhost/login.do" );
let connection  : HttpURLConnection = url.openConnection() as HttpURLConnection;

connection.requestMethod    = "POST";
connection.requestProperty["Accept-Language"] = "ja";
connection.doOutput         = true;

let writer : PrintWriter;
let reader : BufferedReader;

writer = new PrintWriter( connection.getOutStream() );
writer.print( "id=test&pass=test" );
writer.close();

reader = new BufferedReader( new InputStreamReader( connection.getInputStream() ) );
while ( ( line = reader.readLine() ) != null ) {
    console.println( line );
}
reader.close();
connection.disconnect();