OM AXI - The server does not respond to the request

Hi.
Our client has Mitel as local server.
We want to send messages from our server to Mitel via SIP-DECT OM Application XML.
Our server is written in Java.
I try to connect to Mitel server using HTTPClient but we don’t get any response from the server.
Moreover, an attempt to connect using curl was also unsuccessful:

........
 curl -k -X POST https://mitel-server-ip:12622 -H "Content-Type: application/xml" -H "Accept: application/xml" -d "<Open username="user-name" password="*****"/>"
 curl: (52) Empty reply from server
........

Could you help solve this problem?

The code looks like this:

.............
            Optional<String> result = Optional.empty();
            try {
                MitelResponseHandler responseHandler = new MitelResponseHandler();

                HttpPost httpPost = new HttpPost(hostName);

                StringEntity stringEntity = new StringEntity(messageXML, ContentType.TEXT_XML.withCharset(StandardCharsets.UTF_8));
                httpPost.setEntity(stringEntity);
                httpPost.addHeader("Accept", "application/xml");
                httpPost.addHeader("Content-Type", "application/xml");

                logger.info("Mitel Dect:\t\t-----send message---:\n---{}---", httpPost.getRequestLine());

                String responseMessage = httpClient.execute(httpPost, responseHandler);
                logger.info("Mitel Dect:\t\t-----get response---:\n---{}---", responseMessage);

                if (responseMessage != null) {
                    logger.info("Mitel Dect:\t\treceived content :\n--{}--", responseMessage);
                    result = Optional.of(responseMessage);
                }
            } catch (Throwable e) {
                logger.error("Mitel Dect:\t\tError while sending message :\n--{0}--", e);
            }
            return result;
    .......................

The log contains the following entries:

 .......................
	DEBUG InternalHttpClient:164 - ex-0000000001 preparing request execution
	DEBUG RequestAddCookies:122 - ex-0000000001 Cookie spec selected: strict
	DEBUG ProtocolExec:164 - ex-0000000001 target auth state: UNCHALLENGED
	DEBUG ProtocolExec:170 - ex-0000000001 proxy auth state: UNCHALLENGED
	DEBUG ConnectExec:117 - ex-0000000001 acquiring connection with route {s}->https://mitel-server-ip:12622
	DEBUG InternalHttpClient:101 - ex-0000000001 acquiring endpoint (3 MINUTES)
	DEBUG PoolingHttpClientConnectionManager:255 - ex-0000000001 endpoint lease request (3 MINUTES) [route: {s}->https://mitel-server-ip:12622][total available: 0; route allocated: 0 of 5; total allocated: 0 of 25]
	DEBUG PoolingHttpClientConnectionManager:277 - ex-0000000001 endpoint leased [route: {s}->https://mitel-server-ip:12622][total available: 0; route allocated: 1 of 5; total allocated: 1 of 25]
	DEBUG PoolingHttpClientConnectionManager:307 - ex-0000000001 acquired ep-0000000000
	DEBUG InternalHttpClient:116 - ex-0000000001 acquired endpoint ep-0000000000
	DEBUG ConnectExec:124 - ex-0000000001 opening connection {s}->https://mitel-server-ip:12622
	DEBUG InternalHttpClient:156 - ep-0000000000 connecting endpoint (3 MINUTES)
	DEBUG PoolingHttpClientConnectionManager:392 - ep-0000000000 connecting endpoint to https://mitel-server-ip:12622 (3 MINUTES)
	DEBUG DefaultHttpClientConnectionOperator:145 - http-outgoing-0 connecting to /mitel-server-ip:12622
	DEBUG SSLConnectionSocketFactory:211 - Connecting socket to /mitel-server-ip:12622 with timeout 3 MINUTES
	DEBUG SSLConnectionSocketFactory:267 - Enabled protocols: [TLSv1.3, TLSv1.2]
	DEBUG SSLConnectionSocketFactory:268 - Enabled cipher suites: [TLS_AES_256_GCM_SHA384, TLS_AES_128_GCM_SHA256, TLS_CHACHA20_POLY1305_SHA256, TLS_ECDHE_ECDSA_WITH_AES_256_GCM_SHA384, TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256, TLS_ECDHE_ECDSA_WITH_CHACHA20_POLY1305_SHA256, TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384, TLS_ECDHE_RSA_WITH_CHACHA20_POLY1305_SHA256, TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256, TLS_DHE_RSA_WITH_AES_256_GCM_SHA384, TLS_DHE_RSA_WITH_CHACHA20_POLY1305_SHA256, TLS_DHE_DSS_WITH_AES_256_GCM_SHA384, TLS_DHE_RSA_WITH_AES_128_GCM_SHA256, TLS_DHE_DSS_WITH_AES_128_GCM_SHA256, TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA384, TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384, TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256, TLS_DHE_RSA_WITH_AES_256_CBC_SHA256, TLS_DHE_DSS_WITH_AES_256_CBC_SHA256, TLS_DHE_RSA_WITH_AES_128_CBC_SHA256, TLS_DHE_DSS_WITH_AES_128_CBC_SHA256, TLS_ECDH_ECDSA_WITH_AES_256_GCM_SHA384, TLS_ECDH_RSA_WITH_AES_256_GCM_SHA384, TLS_ECDH_ECDSA_WITH_AES_128_GCM_SHA256, TLS_ECDH_RSA_WITH_AES_128_GCM_SHA256, TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA384, TLS_ECDH_RSA_WITH_AES_256_CBC_SHA384, TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA256, TLS_ECDH_RSA_WITH_AES_128_CBC_SHA256, TLS_ECDHE_ECDSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA, TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA, TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA, TLS_DHE_RSA_WITH_AES_256_CBC_SHA, TLS_DHE_DSS_WITH_AES_256_CBC_SHA, TLS_DHE_RSA_WITH_AES_128_CBC_SHA, TLS_DHE_DSS_WITH_AES_128_CBC_SHA, TLS_ECDH_ECDSA_WITH_AES_256_CBC_SHA, TLS_ECDH_RSA_WITH_AES_256_CBC_SHA, TLS_ECDH_ECDSA_WITH_AES_128_CBC_SHA, TLS_ECDH_RSA_WITH_AES_128_CBC_SHA, TLS_RSA_WITH_AES_256_GCM_SHA384, TLS_RSA_WITH_AES_128_GCM_SHA256, TLS_RSA_WITH_AES_256_CBC_SHA256, TLS_RSA_WITH_AES_128_CBC_SHA256, TLS_RSA_WITH_AES_256_CBC_SHA, TLS_RSA_WITH_AES_128_CBC_SHA, TLS_EMPTY_RENEGOTIATION_INFO_SCSV]
	DEBUG SSLConnectionSocketFactory:272 - Starting handshake
	DEBUG SSLConnectionSocketFactory:58 - Secure session established
	DEBUG SSLConnectionSocketFactory:59 -  negotiated protocol: TLSv1.3
	DEBUG SSLConnectionSocketFactory:60 -  negotiated cipher suite: TLS_AES_256_GCM_SHA384
	DEBUG SSLConnectionSocketFactory:70 -  peer principal: CN=OpenMobility Manager, OU=Mobility & Infrastructure, O=Mitel Deutschland GmbH, L=Berlin, ST=Berlin, C=DE
	DEBUG SSLConnectionSocketFactory:83 -  issuer principal: CN=Mitel Deutschland Secure Server Root CA, O=Mitel Deutschland GmbH, L=Berlin, ST=Berlin, C=DE
	DEBUG DefaultHttpClientConnectionOperator:151 - http-outgoing-0 connection established our-server-ip:58442<->mitel-server-ip:12622
	DEBUG PoolingHttpClientConnectionManager:404 - ep-0000000000 connected http-outgoing-0
	DEBUG InternalHttpClient:160 - ep-0000000000 endpoint connected
	DEBUG MainClientExec:102 - ex-0000000001 executing POST / HTTP/1.1
	DEBUG InternalHttpClient:210 - ep-0000000000 start execution ex-0000000001
	DEBUG PoolingHttpClientConnectionManager:581 - ep-0000000000 executing exchange ex-0000000001 over http-outgoing-0
	DEBUG headers:200 - http-outgoing-0 >> POST / HTTP/1.1
	DEBUG headers:203 - http-outgoing-0 >> Accept: application/xml
	DEBUG headers:203 - http-outgoing-0 >> Content-Type: application/xml
	DEBUG headers:203 - http-outgoing-0 >> Accept-Encoding: gzip, x-gzip, deflate
	DEBUG headers:203 - http-outgoing-0 >> Content-Length: 50
	DEBUG headers:203 - http-outgoing-0 >> Host: mitel-server-ip:12622
	DEBUG headers:203 - http-outgoing-0 >> Connection: keep-alive
	DEBUG headers:203 - http-outgoing-0 >> User-Agent: Apache-HttpClient/5.1.3 (Java/17.0.3)
	DEBUG wire:92 - http-outgoing-0 >> "POST / HTTP/1.1[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "Accept: application/xml[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "Content-Type: application/xml[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "Accept-Encoding: gzip, x-gzip, deflate[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "Content-Length: 50[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "Host: mitel-server-ip:12622[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "Connection: keep-alive[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "User-Agent: Apache-HttpClient/5.1.3 (Java/17.0.3)[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "[\r][\n]"
	DEBUG wire:92 - http-outgoing-0 >> "<Open username="user-name" password="*****"/>[\n]"
	DEBUG wire:106 - http-outgoing-0 >> "[0x0]"
	DEBUG wire:92 - http-outgoing-0 << "<OpenResp ommStbState="OK" ommStbAddr="OM-STP-ADRESS" ommVersion="OpenMobility Manager SIP-DECT 9.1SP1-JD10" axiVersion="210517" ommAxiSpecVersion="8.3 (210517)" protocolVersion="53" cloudId="001F1040A508" ommStream="ffsip" axiClients="7" EULAConfirm="true" uptime="18168051" minPPSwVersion1="5.00.SP5" minPPSwVersion2="7.3.3" minPPSwVersion3="7.8.2" minPPSwVersion4="9.0.0" haveEnrolmentPP="1" haveLocating="1" haveDECTPpSettings="1" havePagingAreas="1" haveOMP="true" haveUMO="1" sari="" haveRFPOMM="1" ommPlatform="rfp" GDPREnabled="false" GDPRComplianceText=""><permission>AllCnfRead</permission><permission>AllCnfWrite</permission><permission>Messaging</permission><permission>InfoMessaging</permission><permission>Monitoring</permission><publicKey modulus="ABCDABCD" exponent="00000001"/><accountState id="0" username="user" state="notChanged"/><accountState id="1" username="user-name" state="changed"/><accountState id="2" username="root" state="changed"/></OpenResp>[\n]"
	DEBUG wire:106 - http-outgoing-0 << "[0x0]"
	DEBUG LenientHttpResponseParser:88 - Garbage in response: <OpenResp ommStbState="OK" ommStbAddr="OM-STP-ADRESS" ommVersion="OpenMobility Manager SIP-DECT 9.1SP1-JD10" axiVersion="210517" ommAxiSpecVersion="8.3 (210517)" protocolVersion="53" cloudId="001F1040A508" ommStream="ffsip" axiClients="7" EULAConfirm="true" uptime="18168051" minPPSwVersion1="5.00.SP5" minPPSwVersion2="7.3.3" minPPSwVersion3="7.8.2" minPPSwVersion4="9.0.0" haveEnrolmentPP="1" haveLocating="1" haveDECTPpSettings="1" havePagingAreas="1" haveOMP="true" haveUMO="1" sari="" haveRFPOMM="1" ommPlatform="rfp" GDPREnabled="false" GDPRComplianceText=""><permission>AllCnfRead</permission><permission>AllCnfWrite</permission><permission>Messaging</permission><permission>InfoMessaging</permission><permission>Monitoring</permission><publicKey modulus="ABCDABCD" exponent="00000001"/><accountState id="0" username="user" state="notChanged"/><accountState id="1" username="user-name" state="changed"/><accountState id="2" username="root" state="changed"/></OpenResp>
	DEBUG PoolingHttpClientConnectionManager:428 - Closing expired connections
	DEBUG PoolingHttpClientConnectionManager:428 - Closing expired connections
	DEBUG PoolingHttpClientConnectionManager:428 - Closing expired connections
	DEBUG PoolingHttpClientConnectionManager:428 - Closing expired connections
    .......................