i'm using UDP async socket in C#.net and i want to make the server and a client communicate in different port for sending and receive,
the server send to client with port A and receive from client with port B
the client receive from server with port A and send data to server with port B
is it possible??
In the client bind the socket to port A, and in the client bind to port B. It's as simple as that. The server shouldn't really know A, but get it from the messages it receives messages from the client (using something like ReceiveFrom.
Remember that using UDP, the client has to be the first to send messages, otherwise it's not really a client-server system but more distributed system.
This is exactly how it happens already. The source port for a client is a random port chosen by the OS.
It's not possible to do this, since an endpoint consists of only one IP address and one port number. You would need to use two different sockets and establish two connections with the server in order to use port A and port B.
If you were using TCP rather than UDP as part of the constructor of the TCPClient you can specify which EndPoint you want the outgoing connection to use.
Related
I have a C# Console Application where I'm trying to implement TCP Hole Punching.
I need to listen on a Local Port and at the same time (simultaneously/asynchronously) connect to 2 different remote hosts (in reality a remote hosts public and private endpoints) using the same Local Port.
As I understand I somehow need to bind the Sockets/Ports but I can't figure this out in C#.
There's the TCPListener, TCPClient and Socket classes and I don't know which ones to use to accomplish what I need.
I'm following this guide http://www.bford.info/pub/net/p2pnat/index.html Chapter 4.2
From the same local TCP ports that A and B (Clients) used to register with (Server) S, A and B each asynchronously make outgoing connection attempts to the other's public and private endpoints as reported by S, while simultaneously listening for incoming connections on their respective local TCP ports.
I've already implemented the server part using NodeJS and it's working fine, I'm struggling with the Local Port stuff mentioned above.
I'm pretty sure that TCP only allows a 1-2-1 connection between client and server and ports. The only way to setup the multiple connections is to create two different sockets.
The TCP hole punching you're referring too I have tried before. You need to basically use the relay server to tell both A and B how to connect.. So do as follows:
1) Client A connects to Server on one port
2) Server tells Client B your IP and the port (this will be a new connection you will be setting up, different to your connection to the server)
3) Server tells Client A the IP and Port that Client B will be using
4) Client A uses the info provided to create a new connection directly to client B
5) Client B uses its info about your "new" connection to try and accept the incoming request
6) It might fail to handshake a couple of times due to latency, so build in some sort of repeater to keep trying the connection
7) You eventually should have a direct connection to B
is it possible to have one socket router that would pass incoming sockets to socket servers?
I need this because I want to have multiple servers for handling sockets but only one port for clients to connect to. so if one of the servers goes down, router would send the socket to other healthy socket servers.
Is this even possible and how? or any other solution for my problem?
Yes this is definitely possible, and is used very widespread.
Basically you need to have one TCP server running on that one port you want clients to connect to. Then you can listen for connections. When a connection is established you can reroute packets to other servers (you choose).
Listen on a port with your main server
Accept connections as they come in.
When a connection is opened, read the data in another thread. Take that data and send it to the other server you want to.
Basically, it is a proxy.
I need to bridge traffic from one port (say port 3000) and send it to a new port (say port 4000) and have full bidirectional TCP support.
How should I go about solving this? Should I use the socket class or the TCPClient class?
Would this be as simple as sending the stream of data from one TCPClient to another?
Is there anything else I should be considering?
You program needs to act as both a server and a client:
It should act at a server regarding port 3000, where your program receives connections. Each time you receive a new connection you yourself create a new connection to the actual server on port 4000. Keep these two connections (the one initiated on port 3000 and the one you created to port 4000) together, so you know they are a pair. When you receive data on any of these connection, just send it on the the other connection in the pair.
I have a custom TCP Server listening on port 5888(dummy port). The proxy server listens for incoming connections. When the proxy receives HTTP request for certain pages, it should relay it to the main server on port 80.For other page requests the proxy is required to send data to the main Server on port 8081.
The port 80 is used to service the HTML Pages where as the port 8081 is used for streaming data to the clients.
I am able to receive the incoming connections on the proxy and then read the data from the clients. After reading the data, I can determine which port to connect to on the main server for sending the data.
I am stuck at deciding how to connect on 2 ports for sending the data from the clients to the Main Server?
In that case you either need 2 socket connection objects to the same IP on the different ports (this is legal), or you have one connection object which reconnects according to the port you have to deal with.
Depending on how often you have to switch connections the latter version might have a huge overhead, plus the first one allows you to send data to both ports virtually simultaneously.
You need to stop thinking of your program as a server. After you have received the connection, read the data, and decided what port to send it to, shift gears and start operating as a client would.
Just open a new connection to "localhost" on either port 80 or 8081 and re-send the data you received as if you were the original client.
Your client is connected to the proxy server on port 5888 so no matter from what real server (Web or streaming) you take the data, you are going to provide the data to the client using port 5888 only.
It seems to be a not so practical solution. I am assuming here that you are trying to achieve a kind of control port and data port structure where one port is controlling the streaming from another port.
Just creating two sockets is sufficient for obtaining data from two servers. Here you will have to manually create a protocol which your client understands as you are going to provide both html and streaming data to the client using single port.
How can I send data from my C# socket program to my clients?
Currently I have two programs, server and client.
I start my server, then my clients connect to server, in this way they are connected together, but now I want to send directly from server to client?
As my client cannot start its own connection, of course I have IP and port of my client, how can I send data from my server to a client with known IP and port?
Thanks.
Since your clients are not computer programs you can control, you really have no chance but to contact them from the server. If your clients can handle TCP communications, you need to treat them as servers, and Connect from the server to each client (open the socket on the server side, and Connect to each client IP and port).
It's possible that your clients understand UDP and not TCP. That is actually going to be easier for you, as you only need to create one UDP socket, and use SendTo to send a data to each client (one SendTo call per client).
Let's just hope your clients aren't stuck on the Ethernet level...
I would say that COM-ports are slightly easy to communicate than implementing TCP/IP protocol on your device. Could your device read/write its COM-port?