I want to write a java(SE) program to connect to a proxy server, lets say 123.123.123.123:8080. How am I going to achieve that? What is the protocol between my machine and the proxy server? What is the Java framework's class could be in use?
since java 1.5,you can use java.net.Proxy class to create proxy.
Proxy proxy=new Proxy(Proxy.Type.HTTP, new InetSocketAddress("123.123.123.123", 8080);
URL url = new URL("http://www.example.com");
HttpURLConnection uc = (HttpURLConnection)url.openConnection(proxy);
uc.connect();
reference
The definitive reference for network proxy configuration in Java 5 is this Java Networking and Proxies page.
Yes proxy server is a web server...
Whenever u send a request through your browser to get some resource in the particular web server(say www.google.com),the request is send to the proxy server instead to sending the request directly to the google server..the proxy server process this request,send them to the gooogle server,receives the response and then send the response back to the browser.
Proxy server is basically used to corporate fields to restrict the accesss to specific websites,to keep a track of the internet used by a particular associate,Also it saves some commoonly used webpages in a cache file,so that when another request comes,then instead of connecting to the required server,it get the webpage fron the cache file..Hence it saves the time.Also it scans the incoming data from any server for malware before submitting it to the client(browser).To check if ur company is using proxy server,u can go to the internet explorer setting ->Connections ->LAN Settings
Related
I wrote Java code to login to Salesforce and ran this code on a firewalled server. For this, I have to specify the proxy url and proxy port before connecting to Salesforce due to the firewall. However, I'm getting an unknownhostexception error for the proxy url. If I try to login via curl with the proxy settings, I am able to connect. How come there is a problem connecting using Java then? Any help is appreciated.
Apparently the issue was caused by JVM configs. We have to configure JVM to use the proxy settings as follows:
System.setProperty("http.proxyHost", crmProxyURL);
System.setProperty("http.proxyPort", crmProxyPort);
Depending on your HTTP library the System settings might not be enough or not needed. In the Salesforce context it is quite possible that one would try using the Jetty HTTP Client. In this case the System properties are ignored and proxy needs to be handled by the Jetty client:
ProxyConfiguration proxyConfig = httpClient.getProxyConfiguration();
HttpProxy proxy = new HttpProxy("proxyHost", proxyPort);
proxyConfig.getProxies().add(proxy);
The Apache HTTP Client, another popular choice, also uses its own little mechanism:
HttpHost proxy = new HttpHost("proxyHost", proxyPort, "https");
RequestConfig config = RequestConfig.custom().setProxy(proxy).build();
HttpGet request = new HttpGet(someURL);
request.setConfig(config);
Interesting here: one can specify to use http or https as the proxy protocol.
In general I found using one of the http client much easier that the JDK low level functions.
I was using Jersey 2.25 client with Jackson, I configured everything correctly in Jersey, it worked normally on my development machine when I ran it in a test class, but Jersey client could never connect to a certain host that we have when deployed on our STG environment and always throws a read timeout exception.
I also know that the problem is not in our environment because I can connect using curl
But when switched to HTTPClient it worked normally.
This is how we created our Jersey Client:
Client client = ClientBuilder.newBuilder()
.register(JacksonFeature.class)
.property(ClientProperties.CONNECT_TIMEOUT,5000)
.property(ClientProperties.READ_TIMEOUT,15000)
.build();
The only difference here is the flow of the app, and also the major change that happens in the flow that could affect the connection is that somewhere before calling the Jersey client another class sets a proxy in the system config:
System.setProperty("http.proxyHost",strProxyHost);
System.setProperty("http.proxyPort",strProxyPort);
System.setProperty("https.proxyHost",strProxyHost);
System.setProperty("https.proxyPort",strProxyPort);
However we can establish a connection normally using HTTPClient:
HttpConnectionManagerParams params = new HttpConnectionManagerParams();
params.setConnectionTimeout(5000);
params.setSoTimeout(10000);
HttpConnectionManager manager = new SimpleHttpConnectionManager();
manager.setParams(params);
HttpClient httpClient = new HttpClient(manager);
We are using HTTPClient 3 because part of this app is legacy and we cannot update the version, but it works normally.
What could be causing this connection problem with Jersey? is there something global that Jersey reads when it's trying to connect?
Jersey by default uses HttpURLConnection and HttpURLConnection uses following global settings for proxy configuration -
System.setProperty("http.proxyHost",strProxyHost);
System.setProperty("http.proxyPort",strProxyPort);
System.setProperty("https.proxyHost",strProxyHost);
System.setProperty("https.proxyPort",strProxyPort);
It means if these system variables are set, Jersey will send all the requests through this configured proxy. Check Details here
However, Apache HttpClient does not follow these settings. For using proxy in Apache HttpClient, you have to use HostConfiguration class. Check details here
So, now to your problem, It looks that your STG environment is not able to connect to specified proxy but able to connect with the service directly.
So, while using Jersey, client is not able to connect to proxy and hence ReadTimeoutException is occurring. Since, you haven't configured HttpClient for using any proxy, it is able to connect with the service directly.
For getting the blob container details we are using the below mentioned REST API.
Vhd is the blob container name.
https://(storageAccountName).blob.core.windows.net/vhd?restype=container&comp=list
When we use proxy server details (example:SQUID Proxy) to access the storage REST API calls, we are getting the below mentioned error.
HttpResponse for Blobs:: ResourceNotFoundThe
specified resource does not exist.
RequestId:6dc7e6f2-0001-000d-30f9-d56eb3000xxx
If we access the same rest api without proxy server, we are getting the valid response and it's working.
Per my experience, normally, using squid is as reverse proxy for backend services, but here you want to access the storage REST APIs via squid as forward proxy. You can refer to the wiki page https://en.wikipedia.org/wiki/Proxy_server, the SO thread Difference between proxy server and reverse proxy server and the blog to know the differences between both.
So the solution for the issue is that configuring the proxy server as forward proxy.
For Squid, you can try to refer to the squid wiki pages http://wiki.squid-cache.org/SquidFaq/ConfiguringSquid and http://wiki.squid-cache.org/Features/HTTPS to know how to configure as forword proxy with HTTPS.
For Apache, you can try to refer to the apache doc page http://httpd.apache.org/docs/2.0/mod/mod_proxy.html#forwardreverse to do.
Then, setting the system properties for Java to enable proxy support after setting up forward proxy successfully.
There are two ways support proxy for Java.
Command Line JVM Settings: The proxy settings are given to the JVM via command line arguments:
java -Dhttp.proxyHost=proxyhostURL -Dhttp.proxyPort=proxyPortNumber -Dhttp.proxyUser=someUserName -Dhttp.proxyPassword=somePassword HelloWorldClass
Setting System Properties in Code: Adding the following lines in your Java code so that JVM uses the proxy to make HTTP calls.
System.setProperty("http.proxyPort", "someProxyPort");
System.setProperty("http.proxyUser", "someUserName");
System.setProperty("http.proxyPassword", "somePassword");
System.setProperty("http.proxyHost", "someProxyURL");
More information for Networking & Proxies & Properties in Java, Please refer to http://docs.oracle.com/javase/7/docs/technotes/guides/net/proxies.html and http://docs.oracle.com/javase/7/docs/technotes/guides/net/properties.html.
we got the solution. The issue is we are invoking asynchronous calls for all storage accounts at a time. For example : if we have 5 storage accounts and each storage accounts 5 vhd containers and in for loop if we invoke all 5 at time and with callback waiting for 5 response,In this case it's not working. so we are invoking each call separately and it's started working.
I'm having problems with the URL callback for Google Calendar for a Java web application. I followed the docs successfully and got this working locally but I am now trying to run this on an EC2 instance.
The quickstart tutorial on Google says to select Application Type as 'other'. This worked fine for me locally.
However, when I try and run this on a server I am given the URL to follow in the logs and the URL has a callback with localhost over a different port every time. Since the app was no longer running on localhost, the callback was never received.
After some reading, I need to set the credentials to be 'web application' when actually running this on a web server. This states that I need to define a 'Authorised redirect URIs' and needs to have the correct port.
I was using the following, based on the tutorial for the redirect to the URL to authenticate the user:
Credential credential = new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver()).authorize("user");
After reading this SO post I then set the port in code so I could enter the same port in the credentials to then go into the client_secret.json (my app is currently running on 8080)
I am doing this via:
Credential credential = new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver.Builder().setPort(8080).build()).authorize("user");
However, this throws a bind exception since obviously the port is already in use.
Choosing a port I know is free (I tried 9999) does take me through to the page to allow me to authenticate which makes sense since the URI matches the one stated in the client_secret.json. This then throws a socket bind failure exception:
Caused by: java.lang.Exception: Socket bind failed: [730048] Only one
usage of each socket address ( protocol/network address/port) is
normally permitted.
A lot of examples I have seen online have not set the port, which then allows the AuthorizationCodeInstalledApp to pick a free port but how will this work when we need to specify the Authorised redirect URIs in the API Credentials?
I found the solution for this. I actually had something else running on port 9999 which is why the above didn't work locally. The AuthorizationCodeInstalledApp builder has a setHost() method which works for the EC2 instance.
Credential credential = new AuthorizationCodeInstalledApp(flow, new LocalServerReceiver.Builder().setHost(REDIRECT_URI).setPort(9999).build()).authorize("user");
I'm trying to validate an SSL connection to an http server through a proxy server. In my case, I have 4 pieces of information which are all supplied by the user, and which I'd like to validate explicitly: target host, target port, proxy host, proxy port. I'd prefer to NOT make an actual HTTP request in order to do this validation, since that requires 2 more pieces of information: a request method, and a path (ie. "GET /"). I'd really like to be able to use the HttpClient library because it supports NTLM proxy auth.
I suppose what I want is to get the response of a CONNECT request sent to the proxy server, as all it requires are the 4 pieces of information I have (plus any proxy creds). However this seems to be an implicit request, the result of which is not available to the library client (unless it returns a 407 status code). Is there some way to trigger the CONNECT request explicitly?
You can use ProxyClient shipped with Apache HttpClient. It does precisely that.