I am running a 3rd party product, on Windows 2008 Server, which listens for Incoming connections on port 56600/tcp. The incoming connections are from devices which are trying to report any errors that they may have. These devices are on a (different) 3rd party run network, and port 56600 is enabled between my company's network and the 3rd party network in both directions.
Some devices are able to report their errors on port 56000, but the majority of devices' incoming connections get stuck in the SYN_RECEIVED state and never get properly ESTABLISHED, and so are unable to report errors.
Where should I look to diagnose and correct the problem?
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if when i try to connect with webRTC from outside the local network, it uses a STUN server to exchange info like ip address, port..., and then once the two clients know each other they will directly connect, but the thing is, if any router by default blocks any port that's opened exept for 80, then how do the two clients connect, on what port?
WebRTC is an open framework and does not dictate how the connections are established between the communicating peers. Establishing the connection itself involves the following.
1-The peer discovery is made via Signaling for doing SDP exchanges and exchanging remote host identities. The Signaling can be done over any transport – UDP/TCP, any protocol and via any standard (SIP/XMPP) or custom application level protocol over HTTP/WebSockets etc. The choice of Ports for signalling traffic is left open to the application developer.
2-Once the peer discovery is complete, and the PeerConnections are established at each endpoints, the media data can be sent. Depending on the network topology of the Peers (whether they are in the same host network, or they are in different network (behind Nated IP address), they can choose to connect such that the media traffic is sent over UDP or over TCP. For a more protected environment, the peers may even need a TURN server to relay the media traffic on Peers behalf. Here again, the choice of Media Ports is left open and can be decided via the end application.
I found this on web I hope its helpful
Can software respond to a Wake-on-Lan packet, or does it get filtered out by the NIC and/or OS?
My PC receives a Wake-on-Lan packet when one of my devices can't connect to the service it's expecting. If the PC is off, the packet will cause the machine to boot up, as expected. Unfortunately, it's possible (and common) for a PC user to quit the service manually. This leaves the system in a bad state where the machine is on but the service isn't running.
This particular service (Steam Big Picture Mode) doesn't have a 'run as service' option, and doesn't provide any other hooks to start it remotely. I'd like to write some bootstrap code that listens for the WoL packet and launches the service.
I want to honor the user's request to close the service on the host, up until the point that the WoL request is received. Thus, I'd prefer not to write a process that just monitors the service health and re-starts it when it's closed.
I'm receiving lots of information per client, and i don't know how to handle it. If i make lots of connections to one port will it work? Now, I'm using 1000 ports open with only one client. Do I change?
Typically, one application or one major part of application should have its own port. For each client that connects to the port, you spawn a process/create a thread to service it. After the service is complete and the reply sent back, if connection is not persistent, you close it.
After all, you can only have 65535 ports open on your pc (theoretically), and not all of those are available for private (non system) applications either.
So the way to go is to have one port for application/major application functionality. E.g.
Database Management Systems (e.g. DB2) can have a (theoretical) max limit of 64000 connections per port.
http://pic.dhe.ibm.com/infocenter/pim/v6r0m0/index.jsp?topic=%2Fcom.ibm.wpc.adm.doc%2Fdata_admin%2Fwpc_con_managedb2connections.html
Multiple clients can connect to the same listening port, so you only need to open 1 port in most cases (some protocols, like ftp, use multiple ports). It is the combination of client IP/port and server IP/port that uniquely identifies a connection, so it works just fine. There are multiple programming models available to allow a server to service multiple clients at one time.
I have a simple client application which sends udp datagram to the server with known ip address and port and waits for respond. Client can be started on any computer or mobile device and it can be located behind several routers and firewalls... Server application listens certain port for client's datagram and replies to the client's endpoint with an answer. Server application works on windows computer with properly configured firewall, etc. So, as I understand, this simple scheme should work regardless to client's location and his firewall settings. But it looks like it doesn't work in about 75% of configurations. Server receives request from the client in 100% of cases, but in 75% of cases client can't receive response from the server, i.e. it looks like it's always blocked by something (server attempts 10 times to send an answer to the client, but without luck, i.e. client doesn't receive anything). I tried many different configurations of client computers to figure out the reasons of these issues and what I've found:
In some cases simple windows firewall can block respond packets (But how it could be possible? As I understand, all respond packets must be forwarded back to the client regardless to firewall settings.)
Some Hardware firewalls or NATs also can block respond UDP packets. And again, I can't understand why it could be possible?
The question is - is there any reliable method to deliver an answer to client? As I know, many programs, such as Skype works fine with UDP even with all these network "obstacles".
Thank you!
I want to connect two clients (via TCP/IP sockets). The clients can discover each other using an intermediate server. Once the clients discover each other, there should not be any involvement of the server.
I made some study about this and found many people suggesting JXTA. But I'd like to create the protocol myself from scratch (because in future I might have to implement the same using WebSockets as well (when my client is a Browser)). Currently, my clients can be Desktop applications or mobile applications.
My questions are:
How will clients discover each other at the server? If the server sends the global IP address of the clients to each other, will that information be enough to create a peer-to-peer connection? What if the clients are on the same LAN network and the server is on a different WAN?
Client have dynamic IP address. Can their IP change all of a sudden even if it has an active socket?
Is peer-to-peer connection is reliable for transfer of non-continuous data (like in chat application)?
[NOTE: by peer-to-peer connection I mean establishing a client-server TCP/IP socket connection (using Java) by making one of the client as temporary socket-server]
Thanks in advance.
1) When the clients connect to the server they will have to notify the server of the port number they will keep open for incoming connections from other clients. The server will know client's IP address. Then the server will need to communicate/send these details to the other party/client. The actual location of the clients does not make any difference. If two clients are on the same network the network routers will find them and make their communication paths shorter.
2) Dynamic IP address can NOT change during active connection - if it does the connection will be dropped and both clients will have to re-initiate the connection through the server in 1)
3) Yes