using System;

using System.Net;

using System.IO;

using System.Net.Sockets;

using System.Text;

using System.Data;

​

public class Program

{

    public static void Main()

    {

        string url = "http://api.openweathermap.org/data/2.5/weather?q=Hanoi&mode=xml&appid=78dff84492be32f8b4f77692904607a1";

        Console.WriteLine(CallViaWebClient(url));

        Console.WriteLine(CallViaTCPClient(url));

    }

    public static string CallViaWebClient(string url)

    {

        WebClient client = new WebClient();

        client.Headers.Add ("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

        Stream data = client.OpenRead(url);

        StreamReader reader = new StreamReader(data);

        string s = reader.ReadToEnd();

        data.Close();

        reader.Close();

        return s;

    }

    public static string CallViaTCPClient(string url)

    {   

        string s ="";

            Uri myUri = new Uri(url);

            IPHostEntry hostEntry;

            string data;

            string result;

            string domain = myUri.Host;

            string geturl = myUri.PathAndQuery;

            hostEntry = Dns.GetHostEntry(domain);

​

            if (hostEntry.AddressList.Length > 0)

            {

                var ip = hostEntry.AddressList[0];

                TcpClient tcpclient = new TcpClient(myUri.Host, 80);

                StreamReader sr = new StreamReader(tcpclient.GetStream());

                StreamWriter sw = new StreamWriter(tcpclient.GetStream());

                data = "GET " + geturl + " HTTP/1.1";

                sw.WriteLine(data);

                sw.Flush();

                data = "Host: " + domain;

                sw.WriteLine(data);

                sw.Flush();

                data = "";

                sw.WriteLine(data);

                sw.Flush();

                while (!sr.EndOfStream)

                {

                    result = sr.ReadLine();

                    s += result + "\r\n";

                }

                sw.Close();

                sr.Close();

                tcpclient.Close();

            }

        return s;

    }

}