.NET (Core and Framework)

void SentMsg(String[] msg, int MsgNum )
{
    try
    {
       String reqURI = "www.xxx.com"
       ASCIIEncoding encoding = new ASCIIEncoding();
 
       HttpWebRequest myReq = (HttpWebRequest)WebRequest.Create(reqURI);
       myReq.Method = "POST";
       myReq.KeepAlive = true;

       foreach (int index in MsgNum)
       {
          String readContent;
          Byte[] byte = encoding.GetBytes(msg[index]);
          myReq.ContentLength = byte.Length;

          Stream requestStream = myReq.GetRequestStream();
          requestStream.Write(byte, 0, byte.Length);
          requestStream.Close();

          HttpWebResponse response = (HttpWebResponse)myReq.GetResponse();

          Strean receiveStream = response.GetResponseStream();
          StreamReader readStream = new StreamReader(receiveStream, Encoding.UTF8);

          readContent = readStream.ReadToEnd();
          Console.Write(readContent);
          readStream.Close();
       }
    }
}