Retrofit unable to resolve host

Android
1

Hello,
I am trying to call an API through retrofits.
The url that I call, is located on a server, in which at this moment I access go VPN.
The token I am sending right now is good.
I have tested everything via postman and it works correctly.
Instead when I call through Android studio I get the exception “retrofit unable to resolve host”.
I have made various changes to the code, according to some examples found on the net, but I can not solve the problem.
If I use the same code to access the public bees of “jsonplaceholder.typicode.com” everything works correctly

    // var urlConnection: String ="http://iswvgenint03/api/"
     var urlConnection: String ="http://172.20.26.375/api/"
     override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)
    var miocontext = this.baseContext


    //  textViewResult= findViewById(R.id.text_view_result);


    val clientBuilder = OkHttpClient.Builder()
    var authTokenBearer ="Bearer eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiJ9.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.nYf6SBlOE0AFEenWD8yLBPewyTQ9kMinCnL5eVEblZ_4CXKSbct-plvoJ7iIpugCdAiTJjiDWD4vNLIQ_ylzp93s8wctHbN2HLbZg_t-20CJwt8HQK0AmOup_jT3ayomGVOym0_ptmJNnzT6ozvmOkuYZtf5OQ0BCNuLJF4oVw1L6-KB0AXdigV-8UPbRehkuVRdTj8V1zrZqlyDGAIqDKm72UkmCtD3PTQASi428ZExSAZnfkiVF1TvloGpaeSPbhMwClX6KO5xr5ZJ9o75sCCrc8Onhtb80w43O3YH02U3PaYFd6TKL7p6ipphszg7kALeAQDSFxuUE9SJ_G3P5w"

        @Throws(IOException::class)
        override fun intercept(chain: Interceptor.Chain): okhttp3.Response? {

            val original = chain.request()
            val request = original.newBuilder()
                .header("Authorization",  authTokenBearer)
                .method(original.method(), original.body())
                .build()

            return chain.proceed(request)


        }
    }
    //Add the interceptor to the client builder.
    clientBuilder.addInterceptor(headerAuthorizationInterceptor)
    val client: OkHttpClient = clientBuilder.build()


    var retrofit = Retrofit.Builder()
        .baseUrl(urlConnection)
        .client(client)
        .addConverterFactory(GsonConverterFactory.create())
        .build()

    val jsonPlaceHolderApi = retrofit.create(JsonPlaceHolderApi::class.java)

    val call = jsonPlaceHolderApi.getClients()

    call.enqueue(object : Callback<List<Client>> {
        override fun onResponse(call: Call<List<Client>>, response: Response<List<Client>>) {
            if (!response.isSuccessful) {
                //    textViewResult.setText("Code: " + response.code())
                return
            }

            val posts = response.body()!!
        }

        override fun onFailure(call: Call<List<Client>>, t: Throwable) {
            Log.d("errot",t.message)
        }
    })

}

in an interface file I have
@GET (“Clients”)
fun getClients (): Call <List >

I arrive always in onFailure

The error messages I get are
java.net.UnknownHostException: Unable to resolve host “iswvgenint03”: No address associated with hostname
if I use the url

java.net.UnknownServiceException: CLEARTEXT communication to 172.20.26.375 not permitted by network security policy
if I use the ip address

I think android studio can’t get to the url via vpn.

Do you have any solution for me?
Thanks

2

I solved it by adding this code to the manifest.xml file

  <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
  <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
  <uses-permission android:name="android.permission.INTERNET" />
  <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />


   android:usesCleartextTraffic="true"

Then chased I found that Retrofit was unable to resolve the url with the VPN so everything worked with the ip address
and finally I modified the call in the interface

from so

    @GET("Clients")
    fun getClients(): Call<ClientList>

to

    @GET("Clients/")
    fun getClients(): Call<ClientList>