I have created my own websocket class that extends the abstract System.Net.WebSockets.WebSocket Class. my class uses TcpListener and TcpClient to communicate. After this server receives an HTTP-Get-formatted request that asks to upgrade to a websocket connection, I am able to complete the handshake successfully and communicate with a websocket client.
Separately I have a simple HTTP server that sends and receives HTTP requests using HttpListener and HTTPClient.
Now I want to combine them.
I would like this HTTP server to, upon receiving a websocket request, transfer the "connection" to my websocket server to handle. However I am struggling to conceptually understand what a TCP "connection" is.
I know that I can create a TCPClient using an existing socket, but I am unsure how to retrieve the existing HTTPListener's socket (maybe it can't be exposed?). And for that matter I am unsure what would happen if I tried to have a TCPClient and HTTPListener sharing the same socket.
So how do I construct a TCPListener from an existing HTTPListener?
However I am struggling to conceptually understand what a TCP
"connection" is.
RFC 793, Transmission Control Protocol (and the subsequent RFCs that update it) is the standard for TCP. It explains what a TCP connection is, and later goes into more detail:
Multiplexing:
To allow for many processes within a single Host to use TCP
communication facilities simultaneously, the TCP provides a set of
addresses or ports within each host. Concatenated with the network and
host addresses from the internet communication layer, this forms a
socket. A pair of sockets uniquely identifies each connection.
That is, a socket may be simultaneously used in multiple connections.
The binding of ports to processes is handled independently by each
Host. However, it proves useful to attach frequently used processes
(e.g., a "logger" or timesharing service) to fixed sockets which are
made known to the public. These services can then be accessed through
the known addresses. Establishing and learning the port addresses of
other processes may involve more dynamic mechanisms.
Connections:
The reliability and flow control mechanisms described above require
that TCPs initialize and maintain certain status information for each
data stream. The combination of this information, including
sockets, sequence numbers, and window sizes, is called a
connection. Each connection is uniquely specified by a pair of
sockets identifying its two sides.
When two processes wish to communicate, their TCP's must first
establish a connection (initialize the status information on each
side). When their communication is complete, the connection is
terminated or closed to free the resources for other uses.
Since connections must be established between unreliable hosts and
over the unreliable internet communication system, a handshake
mechanism with clock-based sequence numbers is used to avoid erroneous
initialization of connections.
Related
I'm looking to enhance a WPF app I have that currently receives/broadcasts UDP datagrams within its network with a bridge functionality to share packets with other instances of the app on different subnets.
I essentially want one instance to connect with another and then be broadcast UDP packets while a connection is maintained. To do this, I figure a TCP connection will work at least for the handshake and periodic acks. However, I do not require the TCP overhead for the data itself, which could be transmitted multiple times per second for hours or longer (however long the two are connected).
Given these requirements does it make sense to do a hybrid where the TCP is used for handshaking/acks but data is sent via UDP (I assume the TCP connection can be configured to be kept open indefinitely), or would the additional overhead of sending the datagrams as TCP payloads be negligible? Or should I implement a syn/ack functionality within the UDP transmission? Is there an established standard for this sort of connection?
I had an argument with a colleague on the selection.
We have two processes running on the same machine.
=> NamedPipe and UDP are KERNEL OBJECT so as far as i understand this is same overhead.
The advantage of UDP is that if tomorrow we will separate those two processes and they will run on two different computers so I do not have to change anything.
I think that the NamedPipe performance are better since there is no need to use a network card to send the information to the same machine (am I right .. sending localhost will use the network card - right ?)
Can anyone advise us please ??
Thanks
Before Implementation , you can care below points :
Named pipes:
Named pipes provide interprocess communication between a pipe server and one or more pipe clients.
They support message-based communication and allow multiple clients to connect simultaneously to the server process using the same pipe name.
Named pipes also support impersonation, which enables connecting processes to use their own permissions on remote servers.
User Datagram Protocol :
User Datagram Protocol (UDP) is a simple protocol that makes a best effort to deliver data to a remote host.
The UDP protocol is a connectionless protocol, UDP datagrams sent to the remote endpoint are not guaranteed to arrive, nor are they guaranteed to arrive in the same sequence in which they are sent.
Applications that use UDP must be prepared to handle missing, duplicate, and out-of-sequence datagrams.
I am designing a server client app in C#.
the client connect and communicate with the sever threw tcp socket.
in the server side I am using the socket.accept() method in order to handle new connection from client. when client is connecting, the server use a random port in order to communicate with the client.
so my question is.. how many clients the server can receive in this kind of form?
is there another form that I should use in order to handle lots of clients?
This is practically limited by the OS. You have to test this. On Windows you must use fully asynchronous socket IO at this scale. You will probably be limited by memory usage.
On a TCP level there is no practical limit. There can be one connection for each combination of (server port, server ip, client port, client ip). So with one server port and one server ip you can serve an unlimited amount of clients as long as they have less than 65k connections per client.
You do not need to pick a random port on the server. This is a common misconception.
in the server side i am using the socket.accept() method in order to handle new connection from client. when client is connecting, the server use a random port in order to communicate with the client.
Not unless you open another, pointless, connection from server to client, and you won't be doing that for firewall reasons. The accepted socket uses the same local port number as the listening socket. Contrary to several answers and comments here.
Your question is therefore founded on a misconception. Whatever you run out of, and it could be memory, thread handles, socket handles, socket buffer space, CPUs, CPU power, virtual memory, disk space, ..., it won't be TCP ports.
EDIT Adherents of the new-random-port theory need to explain the following netstat output:
TCP 127.0.0.4:8009 0.0.0.0:0 LISTENING
TCP 127.0.0.4:8009 127.0.0.1:53777 ESTABLISHED
TCP 127.0.0.4:8009 127.0.0.1:53793 ESTABLISHED
TCP 127.0.0.4:8009 127.0.0.1:53794 ESTABLISHED
TCP 127.0.0.4:8009 127.0.0.1:53795 ESTABLISHED
TCP 127.0.0.4:8009 127.0.0.1:53796 ESTABLISHED
TCP 127.0.0.4:8009 127.0.0.1:53798 ESTABLISHED
TCP 127.0.0.4:8009 127.0.0.1:53935 ESTABLISHED
and show where in RFC 793 it says anything about allocating a new port to an accepted socket, and where in the TCP connect-handshake exchange the new port number is conveyed.
You may like to see this question I asked in similar vein: https://softwareengineering.stackexchange.com/questions/234672/is-there-are-problem-holding-large-numbers-of-open-socket-connections-for-length, and particularly some of the comments.
The answer seems to be that there is no practical limit. The combination of receive port and send port must be unique, and each of them can have 64K values. The total number of combinations is extremely large. There really are servers out there with extremely large numbers of open connections, but to get there you have to solve a number of other interesting problems. The question above contains a link to an article about a million connection server. See also How to retain one million simultaneous TCP connections?. And do a web search for the C10K problem.
What you probably cannot do is use synchronous ports and threads because you run into thread limits, not port limits. You have to use asynchronous ports and a thread pool. And you will have to write one to throw away, just to find out how to do it.
My understanding for now about client-server connections in C#:
TCPListener = Server
TCPClient = Client
In alternative to this exists a "Socket" class which can be used as Client and as Server, but at the end do both variants the same thing?!
I understand the TCPClient. It has a getStream() method, which returns a NetWorkStream which has methods for read and write from/to the stream.
My problem is the TCPListener on the server-side. The TCPListener has not a getStream() method and also no read/write method. How i can read/write from the TCPListener from/to the stream?
TCP supports bidirectional streaming. Once a connection is established, there's not much difference between the client and the server ends.
You would use TcpListener.AcceptTcpClient to establish the connection and give the server side its TcpClient instance.
You mention sending messages in your question title. One important thing to bear in mind is that if you're working at this low level with TCP, there's no inherent "messaging" layer - calls of Send at one end are not matched 1-1 with calls of Receive at the other end. If you want messaging you have to build that yourself on top of these primitives, or switch to a higher level networking library (e.g. WCF) which automatically hides this level of detail.
Basically, the TcpListener class acts along the lines of "I intend to allow people to connect to me" - and calls to Accept* like methods are the way of saying "if anyone's currently asking to connect with me, let's create that connection now and start talking"
TcpListener lets you accept incoming connections using eg. the AcceptTcpClient method. This returns a TcpClient instance you can use for bi-directional communication with the client.
TCP is a protocol built around connections, so you can't really send or receive data without estabilishing a connection first - that applies to both the client and server.
You can use the TcpClient's stream to both receive and send data from/to the client
the TcpListener only listens for requests, it cannot interact with them.
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.