How can solve "Failure in SSL library" when I send params to a Flask web service from Android?

I did try to send some values as "application/json" from Android application to Flask web-service. this is my Java code:

  Thread thread = new Thread(new Runnable() {
        @Override
        public void run() {
            try {
                URL url = new URL("https://192.168.43.31:5000/a/");
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                conn.setRequestMethod("POST");
                conn.setRequestProperty("Content-Type", "application/json;charset=UTF-8");
                conn.setRequestProperty("Accept","application/json");
                conn.setDoOutput(true);
                conn.setDoInput(true);
                JSONObject jsonParam = new JSONObject();
                jsonParam.put("name", name);
                Log.i("JSON", jsonParam.toString());
                DataOutputStream os = new DataOutputStream(conn.getOutputStream());
                //os.writeBytes(URLEncoder.encode(jsonParam.toString(), "UTF-8"));
                os.writeBytes(jsonParam.toString());
                os.flush();
                os.close();
                Log.i("STATUS", String.valueOf(conn.getResponseCode()));
                Log.i("MSG" , conn.getResponseMessage());
                conn.disconnect();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    });
    thread.start();

python code:

    #!flask/bin/python
    from flask import Flask , request


       app = Flask(__name__)
       @app.route('/a/', methods=['GET', 'POST'])
       def get_request1():

          data = request.data


       if __name__ == '__main__':
           app.run(host="0.0.0.0",debug=True, port=5000)

but it shows this error (flask):

so I did track the error on android and I found this error:

I/System.out: open:https://192.168.43.31:5000/a/
I/JSON: {"name":"gshzj"}
D/libc-netbsd: [getaddrinfo]: hostname=192.168.43.31; servname=(null); cache_mode=(null), netid=0; mark=0
           [getaddrinfo]: ai_addrlen=0; ai_canonname=(null); ai_flags=4; ai_family=0
I/System.out: [CDS][DNS] getAllByNameImpl netId = 0
D/libc-netbsd: [getaddrinfo]: hostname=192.168.43.31; servname=(null); cache_mode=(null), netid=0; mark=0
           [getaddrinfo]: ai_addrlen=0; ai_canonname=(null); ai_flags=4; ai_family=0
I/System: core_booster, getBoosterConfig = false
I/System.out: [CDS]rx timeout:0
I/System.out: [socket][0] connection /192.168.43.31:5000;LocalPort=34295(0)
          [CDS]connect[/192.168.43.31:5000] tm:90
D/Posix: [Posix_connect Debug]Process com.sourcey.materialloginexample :5000 
I/System.out: [socket][/192.168.43.1:34295] connected
I/System: core_booster, getBoosterConfig = false
D/libc-netbsd: [getaddrinfo]: hostname=192.168.43.31; servname=(null); cache_mode=(null), netid=0; mark=0
           [getaddrinfo]: ai_addrlen=0; ai_canonname=(null); ai_flags=4; ai_family=0
D/Surface: Surface::setBuffersDimensions(this=0xb45af700,w=720,h=1184)
V/NativeCrypto: SSL handshake aborted: ssl=0xaf8326c8: Failure in SSL library, usually a protocol error
            error:100000f7:SSL routines:OPENSSL_internal:WRONG_VERSION_NUMBER (third_party/openssl/boringssl/src/ssl/tls_record.cc:242 0x9b4bb9fe:0x00000000)
D/Surface: Surface::setBuffersDimensions(this=0xb45af700,w=720,h=1184)
I/System.out: [CDS]close[34295]
          Close in OkHttp
I/System: core_booster, getBoosterConfig = false
I/System.out: [CDS]rx timeout:0
          [socket][1] connection /192.168.43.31:5000;LocalPort=36619(0)
          [CDS]connect[/192.168.43.31:5000] tm:90
D/Posix: [Posix_connect Debug]Process com.sourcey.materialloginexample :5000 
I/System.out: [socket][/192.168.43.1:36619] connected
I/System: core_booster, getBoosterConfig = false
I/System.out: [CDS]close[36619]
W/System.err: javax.net.ssl.SSLHandshakeException: No enabled protocols; SSLv3 is no longer supported and was filtered from the list
W/System.err:     at com.google.android.gms.org.conscrypt.NativeSsl.initialize(:com.google.android.gms@[email protected] (020306-194189626):7)
              at com.google.android.gms.org.conscrypt.ConscryptFileDescriptorSocket.startHandshake(:com.google.android.gms@[email protected] (020306-194189626):6)
              at com.android.okhttp.Connection.upgradeToTls(Connection.java:201)
              at com.android.okhttp.Connection.connect(Connection.java:155)
              at com.android.okhttp.internal.http.HttpEngine.connect(HttpEngine.java:282)
              at com.android.okhttp.internal.http.HttpEngine.sendRequest(HttpEngine.java:216)
              at com.android.okhttp.internal.http.HttpURLConnectionImpl.execute(HttpURLConnectionImpl.java:392)
              at com.android.okhttp.internal.http.HttpURLConnectionImpl.connect(HttpURLConnectionImpl.java:107)
              at com.android.okhttp.internal.http.HttpURLConnectionImpl.getOutputStream(HttpURLConnectionImpl.java:218)
              at com.android.okhttp.internal.http.DelegatingHttpsURLConnection.getOutputStream(DelegatingHttpsURLConnection.java:218)
              at com.android.okhttp.internal.http.HttpsURLConnectionImpl.getOutputStream(HttpsURLConnectionImpl.java:25)
              at com.sourcey.materiallogindemo.SignupActivity$4.run(SignupActivity.java:218)
              at java.lang.Thread.run(Thread.java:831)

the problem is that SSLv3 is not supported anymore by android, so I did try to remove it using ProviderInstaller.installIfNeeded(getApplicationContext()); at the beginning of the activity but no use. so help and thanks

Solution

You are sending the request as "POST" from your Android application but on Python side, the route you created will accept "GET".

@app.route('/a/', methods=['GET'])

conn.setRequestMethod("POST");

Try changing @app.route('/a/', methods=['GET']) with @app.route('/a/', methods = ['POST'])

Also seems like you are trying to connect to HTTPS:

URL url = new URL("https://192.168.43.31:5000/a/");

Try creating the app instance like below: if __name__ == '__main__': app.run(port=5000, host='0.0.0.0', debug=True, ssl_context='adhoc')

pip install pyopenssl