OkHttpClient client = new OkHttpClient().newBuilder()
  .build();
MediaType mediaType = MediaType.parse("text/plain");
RequestBody body = new MultipartBody.Builder().setType(MultipartBody.FORM)
  .addFormDataPart("sender_id","ETECH")
  .addFormDataPart("destinataire","237673767207")
  .addFormDataPart("message","API SMS ")
  .addFormDataPart("login","243161185")
  .addFormDataPart("password","test1")
  .addFormDataPart("ext_id","12345")
  .addFormDataPart("programmation","0")
  .build();
Request request = new Request.Builder()
  .url("https://sms.etech-keys.com/ss/sendsms.php")
  .method("POST", body)
  .build();
Response response = client.newCall(request).execute();

    /*      Commentaire    

            sender_id:ETECH                 Max 11 Caractère
            destinataire:237673767207       Avec Indicatif
            message:API SMS                 Massage
            login:243161185                 Votre Login
            password:test1                  Votre Password
            ext_id:12345                    l'id du SMS à votre Niveau
            programmation:0                 Delais de retardemment d'envoi en ms

    */