使用するEncodingはUTF-8を仮定しています。 public static void PostData(string host, int port, string data) { try { Uri requestUri = new Uri(string.Format("http://{0}:{1}/", host, port)); WebRequest request = WebRequest.Create(requestUri); request.Proxy = new WebProxy(); request.Method = "POST"; byte[] postDataBytes = Encoding.UTF8.GetBytes(data); request.ContentLength = postDataBytes.Length; using (Stream stream = request.GetRequestStream()) { stream.Write(postDataBytes, 0, postDataBytes.Length); WebResponse response = request.GetResponse(); using (StreamReader reader = new StreamReader(response.GetResponseStream(), Encoding.UTF8)) { string strResp = reader.ReadToEnd(); // Do something... } } } catch (Exception ex) { log.ErrorFormat("Error in {0} method\n{1}", MethodBase.GetCurrentM