Requisites:
I should open multiple sockets/connections to the same server IP and
Port.
I should detect from which connection a request has come and
reroute the response to the same connection
A connection is represented as server Ip and port + client Ip and
port
Each connection has to be single-use=false, it is expected to have multiple request/replies
I'm using collaborating TcpReceivingChannelAdapter and TcpSendingMessageHandler with TcpNetClientConnectionFactory.
And IntegrationFlow for generating those connections dynamically.
How to create multiple sockets for TcpNetClientConnectionFactory that all point to the same Host and port?
I know how to set destination with new TcpNetClientConnectionFactory(host, port). But I'm unable to see or find how to affect which port is used
Should it be done with multiple TcpNetClientConnectionFactory each being bound to one inbound and outbound TCP adapter?
How can I set the local port for those connections? or at least how to obtain it?
I don't seem to find any documentantion about this option. The most similar would be This question
You need a separate connection factory/adapters for each.
See TCP Connection Events.
Use an ApplicationListener or #EventListener to receive TcpConnectionEvents.
The event has getConnectionId() which contains both the local and remote port; the event also has the connection factory bean name.
Or you can cast getSource() to TcpConnection and call getPort() (but you should not otherwise interact with the TcpConnection object.
Related
I see this sort of address used in a bunch of examples. What does it mean exactly? Does it mean it will connect to any/all machines on the subnet that have something listening to that port? Or something else entirely? I see such usage in the docs and in books without explanation. Sort of annoying.
It is explained in the manual.
ZeroMQ supports multiple transports. tcp means you are using the TCP transport.
The address (or endpoint) for the TCP transport has the following format:
tcp://interface:port
When you bind to a local address, interface is either the IP address of a specific interface (network) or *, which means to listen on all interfaces (networks). port is the TCP port or * for a random port.
When you connect to a remote endpoint, interface is the hostname or IP address of the remote machine. port is the TCP port of the remote endpoint.
To add to rveerd's answer, what's often missed is that you can multiply bind a socket. So, tcp://*:5555 specifies port 5555 on any interface and you can bind the socket accordindly. But by calling zmq_bind() again you can bind the same socket to, say, ipc:///tmp/feeds/0, which means it will also accept connections on the /tmp/feeds/0 IPC pipe.
This is a pretty spectacularly useful feature in my view, because you can trvially have other actors local and remote to the machine though a single zmq socket.
I'm currently working on a ABAP Push Channel server to WebSocket client connection and I need the IP-address of the client in order to identify whether this client is the one I want to send the message to. In my scenario there could be multiple WebSocket connections.
Now there is the ssi_websocket_table table and the ssi_websocket_table_row row with the the field caller_ip, however this gives me the IP address of the DNS-Server of the network I'm connected to, and I expected the IP address of my local PC since the WebSocket-client is running on this machine.
Is there any other way to get the clients IP address from an active WebSocket connection in ABAP?
P.S. Looking at all the table entries, it shows the correct IP when using a different server configuration, as soon as I know why that's the case I will report back.
As pointed out by vwegert it makes no sense to use the IP to tell the WebSockets apart, I think it would probably be better to use an ID for each WebSocket connection instead.
You could get the IP from the WebSocket server context which gets the IP header apparently from the opening HTTP handshake for the connection:
DATA(lo_context) = i_context. " IF_APC_WSP_SERVER_CONTEXT type
DATA(lo_request) = lo_context->get_initial_request( ).
" initialize G_CONTEXT_ID_FIELD for PCP_SET_CONTEXT_FIELDS
DATA(lv_id) = lo_request->get_header_field( if_http_header_fields_sap=>remote_addr ).
the sample is taken from the SAP standard class CL_APC_WS_EXT_ABAP_ONLINE_COMM, ON_MESSAGE method.
I'm trying to implement TCP hole punching with windows socket using mingw toolchain. I think the process is right but the hole doesn't seems to take. I used this as reference.
A and B connect to the server S
S sends to A, B's router IP + the port it used to connect to S
S does the same for B
A start 2 threads:
One thread tries connecting to B's router with the info sent by S
The other thread is waiting for an incoming connection on the same port used to connect to its router when it connected to S
B does the same
I have no issue in the code I think since:
A and B does get each other ip and port to use
They are both listening on the port they used to connect to their router when they contacted the server
They are both connecting to the right ip and port but get timed out (code error 10060)
I am missing something ?
EDIT: With the help of process explorer, I see that one of the client managed to establish a connection to the peer. But the peer doesn't seems to consider the connection to be made.
Here is what I captured with Wireshark. For the sake of the example, the server S and the client A are on the same PC. The server S listens on a specific port (8060) redirected to that PC. B still tries to connect on the right IP because it sees that the public address of A sent by S is localhost and therefore uses the public IP of S instead. (I have replaced the public IPs by placeholders)
EDIT 2: I think the confusion is due to the fact that both incoming and outcoming connection request data are transfered on the same port. Which seems to mess up the connection state because we don't know which socket will get the data from the port. If I quote msdn:
The SO_REUSEADDR socket option allows a socket to forcibly bind to a
port in use by another socket. The second socket calls setsockopt with
the optname parameter set to SO_REUSEADDR and the optval parameter set
to a boolean value of TRUE before calling bind on the same port as the
original socket. Once the second socket has successfully bound, the
behavior for all sockets bound to that port is indeterminate.
But talking on the same port is required by the TCP Hole Punching technique to open up the holes !
A start 2 threads:
One thread tries connecting to B's router with the info sent by S
The other thread is waiting for an incoming connection on the same port used to connect to its router when it connected to S
You can't do this with two threads, since it's just one operation. Every TCP connection that is making an outbound connection is also waiting for an incoming connection. You simply call 'connect', and you are both sending outbound SYNs to make a connection and waiting for inbound SYNs to make a connection.
You may, however, need to close your connection to the server. Your platform likely doesn't permit you to make a TCP connection from a port when you already have an established connection from that same port. So just as you start TCP hole punching, close the connection to the server. Bind a new TCP socket to that same port, and call connect.
A simple solution to traverse into NAT routers is to make your traffic follow a protocol that your NAT already has an algorithm for forwarding, such as FTP.
Use Wireshark to check tcp connection request(3-way Handhsake process) is going properly.
Ensure your Listener thread is having select() to de-multiplex the descriptor.
sockPeerConect(socket used to connect Other peer) is FD_SET() in Listener Thread.
Ensure your are checking
int Listener Thread()
{
while(true)
{
FD_SET(sockPeerConn);
FD_SET(sockServerConn);
FD_SET(nConnectedSock );
if (FD_ISSET(sockPeerConect)
{
/// and calling accept() in side the
nConnectedSock = accept( ....);
}
if (FD_ISSET(sockServerConn)
{
/// receive data from Server
recv(sockServerConn );
}
if (FD_ISSET(nConnectedSock )
{
/// Receive data from Other Peer
recv(nConnectedSock );
}
}
}
5.Ensure you are simultaneously starting peer connection A to B and B to A.
6.Start your Listener Thread Prior to Connection to server and Peer and have Single Listener Thread for receiving Server and Client.
not every router supports tcp hole punching, please check out the following paper which explains in detail:
Peer-to-Peer Communication Across Network Address Translators
I have a server application that binds to a port and listens on it. I've set up the router to forward the data on this port to the server.
Now, on the client side, I don't actually bind() the socket to any port, and I usually end up with a different port everytime. In that case, how can I prepare the router to forward that port to the client? Or am I supposed to use bind() with the client socket as well? (I remember reading that you're not supposed to do that.)
Firewalls are usually stateful - meaning if TCP connection request into the protected network is allowed, then the packets back to the client are matched (and passed through) automatically. That is to say you don't worry about the client, just setup port forwarding to the server app.
In order to receive datagrams through an UDP connection I have created an object of type UDPClient.
receivedNotificationSock = new UdpClient();
However once done and on using the receive method:
receivedHostNameBuffer=receivedNotificationSock.Receive(ref receivedNotificationIP);
I am getting an exception saying that I must call the bind method.
But there is no bind method in the UDPClient class.
Could You guys please provide me with the code if possible as to what should be done to overcome this exception.
You need I think to know some more about sockets.
All sockets possess a port number. First, you create a socket - which is almost useless on its own. It just floats there. But then you bind it - you assign it a port number. Now it's useful - now you can send and receive data on it.
Remember, all UDP communications are defined by the quad data set of the IP and port of the source and the IP and port of the destination. A freshly created socket doesn't have an IP address or port; binding gives it an IP address and port.
Unfortunately, I'm not a C# programmer, so I can't properly answer your question. But at least you know why it's important.
Pass the port number into the constructor of your UDP client.
receivedNotificationSock = new UdpClient(21000);
You may need to change firewall settings to allow the bind, though a popup window normally opens when you first run this on your dev machine.
For Socket proramming you need to know the sequence of syscalls you need to do on client side and on the server side.
If you are writting a client :
you open a socket with a socket call.
you then connect to the server port with a connect call
once connect is successful
then you send the request to the server using either a send or sendto or a write
which results in reception of data that you can read using a receive or read
On Server Side
you create a socket
bind it to a port
start listening on the socket for incoming connections from various clients using a listen.
There is a non blocking way of listening for connections as well with a select syscall.
Once the you establish a connection you can essentially read the request and start processing it.
Here's an example in C# that may be useful to you.
http://www.developerfusion.com/article/3918/socket-programming-in-c-part-1/