I need to transfer a file between two computers using https protocol using a java code. I have no idea where to start at. Is transfer using socket the only way ? Do I necessarily need to have a code running on the server and one on the client ?
If you already have https server (apache, IIS...) on the machine you want to download from than you will need only the client. Unless your requirement is to write code for both server AND client.
On a general note: YES, in order to transfer file(s) between 2 computers over https you need BOTH server and client.
Related
I have a VB.NET application that utilises databases in an SQL server. I am currently testing the application on the same computer the server is hosted on.
I connect to the server through the following connection string...
("Data Source = " & Master.CurrentIP.Text & ",1433;Network Library=DBMSSOCN;Initial Catalog=ExcelDM;User ID=" & Master.CurrentUser.Text & ";Password=" & Master.CurrentPass.Text & ";")
"Master.CurrentIP.Text" refers to my public IP address and not my computer's.
Basically, everything works perfectly when I test the application on this computer. I am wondering if I can use this as a test for other computers joining or not. Should I host my server on something that isn't my computer?
To clarify, remote connections is enabled on the server and port forwarding (port # 1433) is open both incoming and outgoing through windows firewall and my router port forwarding settings. All TCP/IP options are open in the SQL configuration manager etc.
Based on your comments, I'd make the following assumptions:
You aren't holding any sensitive data, so security isn't a major concern
You are going to be running this on a LAN (local area network) and not over the web
If that's the case I'd suggest the following:
You are fine testing on your local machine - the connection will work the same over any protocol on local or remote, and given the small amount of data in a D&D campaign, you probably aren't going to be worried about performance even if your application is very chatty with SQL server
Put your connection information in the application configuration file, this is supported in .NET framework with some helper types like ConfigurationManager where you can access connection strings like so:
Config file:
<connectionStrings>
<add name="MyConnection" providerName="System.Data.SqlClient" connectionString="server=somehostname;database=Dungeons;uid=user;password=password" />
</connectionStrings>
c# code
string connectionString = ConfigurationManager.ConnectionStrings["MyConnection"];
See here for more details:
https://learn.microsoft.com/en-us/dotnet/framework/data/adonet/connection-strings-and-configuration-files
Since your friends probably don't want to mess with your SQL server and you are probably not joined to a windows domain, I'd say you are fine with putting secrets (user/pass) in the connection string in the configuration file
I'd not bother with what I said about Windows security - basically the users on the client machines would be used as credentials to the SQL database, this would be a bit more of a headache to configure if you aren't all joined to a domain rather than just embedding a SQL user/pass in the config
** Edit: **
Further to conversation, if you are writing an app that clients will be accessing over the web, using a direct SQL connection is not usually the best idea, but it can work if you can manage your clients/IPs.
Generally, opening your SQL server up to the internet is just asking to be attacked - and unless your SQL server is up to date, this can lead to the host machine being compromised.
At best it's an inconvenience, but if you are using that machine for anything other than D&D data, then you probably don't want someone snooping around on it.
In the case that you don't want to change your application architecture
You can whitelist your clients in SQL server/on the firewall. Since it's only friends (let's say 10-20 people?), you can manage their IPs without too much trouble.
This prevents the general internet from being able to access your server.
You could also use a VPN (either software or on your hardware if your router supports it). This also has the effect of putting your clients on your LAN essentially, removing the need for any firewall config apart from the VPN itself.
In the case you are interested in changing your app architecture
You can use a service based approach. This is what is generally used to secure web-based services - .NET framework supports this with WCF (Windows Communication Foundation).
This allows you to define service contracts that your server/client can adhere to.
The communication protocol/method itself is decided via configuration, so you can change what mechanism is used to communicate between client/server after-the-fact without having to change your application code.
This does require you to write a service layer though - you won't be able to directly access SQL from your client, but it could be a useful learning experience, especially if you are interested in doing work like this in the future.
Read about WCF here:
https://learn.microsoft.com/en-us/dotnet/framework/wcf/whats-wcf
There's also the REST based approach which sits down at the HTTP level, .NET framework can support this via ASP.NET web API.
https://dotnet.microsoft.com/apps/aspnet/apis
... so in short, there are a few options
I'd like to log all SQL that a client app is sending to a remote SQL server I have no access to. I'm thinking of some kind of client side proxy that can log and pass through data. It has to run on the same machine as the client app.
Any ideas appreciated.
SQL Server's protocol, TDS ("Tabular Data Stream") is not encrypted by default, so a trivial packet-forwarder could be used to proxy SQL Server connections and intercept commands (and their responses).
The TDS protocol specification is available from Microsoft's website, you could write your own proxy which can intercept commands that way: https://msdn.microsoft.com/en-us/library/dd304523.aspx?f=255&MSPPError=-2147217396
However, this is a large undertaking. You have other simpler options if you don't need to capture every connection:
If you control your application's source-code, then simply modify all database operations to intercept every SqlCommand's CommandText and Parameter values.
You could skip writing a proxy and instead use native packet-capture, you'll need to use WinPCap: https://www.winpcap.org/
You could also use SQL Server's Profiling features to get a log of every command executed: What are the APIs used by SQL Profiler?
What you are looking is called an SQL Profiler.
In specific - you are looking for an API for one.
I have never used an API of a profiler myself - but this one looks promising.
Also - take a look at this question for another sample.
If you want to have an impression of a working profiler client you can take a look at this answer.
Background
I am using a SparkCore wireless arduino board to connect to a local Node.js server. The server includes a local intranet TCP server that a TCP client programmed onto the SparkCore connects to.
Problem
If I run the server on a different network, the server has a different local IP address. When I do this, I have to reprogram the SparkCore arduino to tell it the new local IP address of the server to connect its TCP client to. This is not ideal for a variety of reasons.
Question
Is there a way to have the client dynamically search for the TCP server or alternatively have the server broadcast to TCP clients in a way that would inform the client of the local IP address to use for the server without initially hardcoding it? I would love to do this in way that did not involve iterating through a bunch of IPs on a specific port to see if a connection is made. That being said, if that's the only way to do this, then so be it.
How is the arduino booting? If it's booting using DHCP, one method would be to provide a customer DHCP option that provided the address of the node.js server. ntp, for instance, can configure itself in a similar way. This has the advantage that the arduino need not be on the same local subnet as the node.js server.
An alternative (slightly disgusting) would be to use an A record within your domain (let's say nodejs.example.com. Configure the local DNS recursive server to explicitly return this value (I am presuming you might have lots of different deployments with lots of different nodejs servers).
A third possibility would be to send out some form of discovery packet, either by broadcast, or better by multicast UDP. Assuming it's on the same LAN, the nodejs server could then reply. Clearly you might need to concern yourself with a rogue server impersonating your nodejs server, and therefore might need to add some security (e.g. use a shared secret, send a random nonce plus the nonce hashed with the shared secret to the server, the server checks the hash, and replies with the answer, the nonce, plus the answer hashed with the shared secret and the nonce, each of which the client then checks).
On a client operation, a file is created on the server and I want to allow the client to download that file.
How can this be done?
You can always bring back the data to the client side with you rpc service sending an object.
You still can have a look here
On my PC I have a small program to run SQL Server queries and gets the results back. I don't want to duplicate the DB on the server, I want to call that program on my PC from the server (The server runs Linux OS).
I was thinking of using a web-service to communicate with my PC (using C# maybe), I can attach my PC to a Dynamic DNS (DDNS like No-IP), so I always request the name of the PC not the IP (in case the router restarted and my PC got a new IP).
What do you think, is there a better way to do that?
The fastest solution will probably be to write a web services API written in C#/VB.NET whatever language you prefer. That API could be as simple as executing a remote ad-hoc sql query (rarely recommended) or as complex as a fully blown API. Obviously, security will be important any you may want to create your own SSL certificates and import them to your Linux server (if you're doing this on the cheap) to make sure that your home machine is the one that is reports it is!