What does it mean when the port scanner says a port is "closed"? What settings or what actions by a non-firewall program would close a port? Are there places in Windows that I can go to define "open" and "closed" ports? Could my DSL provider's software close ports even though it is not a firewall? Is there an MSDN link I should go read? Is there some utility software I could download that would help me open these ports or at least gather info on why they are closed?
When Windows program needs to RECEIVE data from network, it informs Windows that it will use a specific port. If no other program uses this port, Windows marks it as "open" and program can reseive data from it.
So, if you connect to another machine directly, closed port can means one of following:
1. No program was started to wait data on this port.
2. Network is misconfigured or has errors, so Windows can't mark port as "open". In this case examine program log for details.
But on real networks direct computer-to-computer connections are common only inside one small LAN. In most cases, you will meet a chain of servers, routers and firewall between you and target machines. To connect to a remote port all this intermediate machines must FORWARD yor request. If one of them fails by any reason (configuration, sequrity etc.) than your request just don't follow to target machine and port appears "closed".
If you have any other questions about ports -feel free to ask it in our "network administration" forum.
Best regards, Gregor Petrov, Famatech support team.