I am unable to establish a connection to the server of my client server app written in vb 6.0.
This is just because that the server of the app is behind a LAN router and the router of the LAN is not in my access so as to configure it. If it is possible to establish a connection so please let me know how? and if it is not possible than how the programs like team viewer and LogMein can establish a connection.
Ask the person who does administer the router to open the port or to give you a VPN tunnel, or to move the server to a lan with lower security requirements. If you have a good reason for needing this they shouldn't make a fuzz about it.
TeamViewer and LogMeIn rely on central systems under their own control. Both the client and the server make an outgoing connection to the central system that patches them through to each other. So on both sides the firewall only has to allow outgoing connections.
Depending on the router at the server end you might be able to use UPnP in your server to map the port through the NAT router.
See Easy UPnP NAT Traversal for a VB6 discussion of the topic.
Related
So I've seen projects like trojan-go,v2ray-go
They are making their own proxy protocols in user space level. I am trying to do the same thing but I don't know how to redirect network traffic from clients to proxy server.
Basically I don't understand how those tools (or any tool) can redirect internet traffic of the device to a certain server, so when the packets are going to the internet they go to the proxy server first instead of their destination ip address.
How can I do it in golang without dealing with netlink and Iptables?
I know apps like wireguard do this by dealing with layer 3-4 stuff using netlink API but I need to know how apps do it without adding a new network interface.
I'm working on a desktop C++ application which uses OpenSSL sockets (a raw TLS socket, not HTTPS) to communicate with our server.
One of our clients are required to route their traffic through a proxy. The client is using ZScaler in Tunnel with Local Proxy mode.
In theory, it's possible to reconfigure ZScaler to force our traffic through a proxy chosen by ZScaler. However, I want to investigate solutions where our application uses the Windows OS-level proxy settings rather than relying on ZScaler configuration.
I've read this post:
openssl s_client using a proxy
But I'm uncertain whether those answers apply to my situation, because that user didn't mention whether they're using Windows or Linux, and they appear to be talking about an HTTP/HTTPS proxy. Also, that question appears to be asking about the s_client function, rather than simply creating a TLS socket to my server through a "Tunnel with Local Proxy" on Windows.
So, my questions are:
Can OpenSSL be used to open an SSL socket to a server through Tunnel with Local Proxy?
Can we make an OS call to determine the IP/socket for the Tunnel with Local Proxy configuration?
If this is possible, then I have another question: suppose we have a single proxy at 10.100.10.0:5000.
If one user in our client's office opens a socket to our server via their proxy, will a 2nd user be unable to connect from their office because they're bottlenecked at single proxy socket?
Put another way: what is the standard way of implementing proxy-awareness for a Windows application using OpenSSL?
Note: This question was originally posted to Network Engineering stack exchange, but it was closed because it refers to an issue above OSI layer 4.
Note: I'm looking for a solution that does not require administrator permissions on the user PC. I would prefer for our application to discover and use OS-level proxy settings without making any administrative changes to the machine, i.e. by calling netsh.
Can OpenSSL be used to open an SSL socket to a server through Tunnel with Local Proxy?
OpenSSL doesn't do it for you but OpenSSL does not prevent it either. The tunnel has to be established before you do the TLS handshake to the endpoint. Depending on what kind of proxy this is you might need to use a HTTP CONNECT method for this or might need to use the SOCKS protocol or whatever your proxy requires. In case of ZScaler this is likely the HTTP CONNECT method but you need to make sure that the connection to the target IP and port is actually allowed by the security policy.
Once you've established the tunnel to the endpoint using the proxy you can just build the SSL socket on top of the TCP socket for the tunnel. Just do the usual SSL setup (i.e. SSL_new etc) and then associate the SSL object with the existing socket using SSL_set_fd. Then proceed as usual with the handshake, i.e. SSL_connect or similar.
Can we make an OS call to determine the IP/socket for the Tunnel with Local Proxy configuration?
I don't know but Winsock use system proxy settings might answer this part.
If one user in our client's office opens a socket to our server via their proxy, will a 2nd user be unable to connect from their office because they're bottlenecked at single proxy socket?
This should not be a problem. It is perfectly normal to have multiple connections through the proxy.
In short we have two separate servers for our web app. The first one is the main server that uses Websockets for handling "chat rooms", and the second server only handles WebRTC audio chat rooms via Websocket. Both servers use Express to create a HTTPS server, use secure Websocket and the port 443.
I recently encountered a problem where a corporate client's firewall blocked the wss-connection to only the WebRTC server. The error logged in the user's browser was "ERR_CONNECTION_TIMED_OUT", which means the user never connects via Websocket. This has not happened with any other clients.
The Websocket connection works normally between the user and the main server, and no rules have been added to their firewall to use our app.
Has anyone encountered something similar? What kind of a firewall setting might cause this? Could this be a cors problem, since the servers are on their own sub-domains?
The main server could be restricting the type of data sent on port 443, which will use SSL to secure that transmitted data.
Refer to this page for information on the "Well-know port numbers".
The WebRTC audio data may need to be transmitted on its own dedicated port number that has been configured on the main server for this.
The problem was that the main server WebSocket used TCP and the WebRTC server used UDP, and UDP was blocked by corporate firewall on default.
WebRTC should use TCP as a backup, but I'm assuming UDP is still needed for the handshake.
my question is simple
When you send data through TCP/IP protocol with EX:firefox you can receive reply on some random port that the browser listen on, while when i try to use a port for another task like CS Gaming or anything else it don't work unless i use kind of VPN ?
PS: there r no firewall blocking connection and port forwarding from my router didn't work as well.
Browsers are client apps that make outbound connections to web servers. When connecting to a server through a router’s NAT, the NAT takes note of the source and destination IP/port pairs so messages sent back from the server on the same connection are automatically routed to the correct client IP/port.
Browsers also support the websocket protocol. This feature makes it seem like the browser is listening on a specific port. However, in reality, it is initiated on a new connection to the server, a connection which remains open all throughout the websocket communication.
What matters is which peer is behind the NAT — the server or the client. For an outbound connection from a client, it can usually use any random port that is available at the time. For an inbound connection to a server, the server's IP/port must be known ahead of time and be routable. If the server is behind a NAT, the router(s) must be configured to make the server reachable from the other side of the NAT.
The server software can make a UPnP request to ask a router to forward inbound packets to the correct IP/Port. The router, depending on its configuration, may or may not honor such a request. If not, the router has to be configured manually by a network administrator.
i was reading this topic
http://ftp.icm.edu.pl/packages/socks/socks4/SOCKS4.protocol
and what im trying to do is:
i have a client/server application, what im trying to do is to use socks 4 BIND request to bind my server to a remote socks server, and make the clients connect to that socks server and the socks server will make them connect to my server (at least thats how i understand socks BIND request)
but i don't fully understand it (my English is kinda bad), what im asking is, is it possible to do so when i dunno any of the remote IPs of the clients? since the server's BIND request package must contain the address of the remote client and i dont really have than since the clients are from unknown users retrieving status info from my server (or can i use 0 for INANY_ADDR) ?
What you are asking for is not possible with SOCKS, nor is it meant for that purpose. Read the spec again more carefully. The BIND command is meant for use with multi-connection protocols (like FTP), where a primary connection is used to communicate between a client and a server, and BIND facilitates situations where the server needs to connect a secondary connection to the client after the client tells the server where to connect. In that situation, the client would issue a BIND command to SOCKS telling it the server's IP/Port so it only accepts that connection, then send the resulting SOCKS listening IP/Port to the server to connect to.
What you are asking for is better served by using a router with Port Forwarding rules defined. Then you can open a listening port on the router that accepts any inbound connection and forwards it to your app's listening IP/Port. Most modern routers support uPNP (Universal Plug-N-Play) so you can configure the forwarding rules programmably instead of requiring admin access to the router's configuration software.