problem when stopping a TTCPServer with connected customers
lazarus / 38-Networking and Web Programming

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chubb · 2010-05-11 04:57

Hello

I try to use a TCP server, Windows and Linux. My choice is focused on
the TTCPServer.

I managed to use it normally, mode bmThreadBlocking.

When a client connects to my server I keep it in OnAccept function is
called when I received the event of the same name. When the client
disconnects, I lot of my office OnAccept. Up until this no problem.

When I turn off the server and restarts without any client connected
to him, everything goes well. By cons, if I switch off the server when
a client is connected, the client is connected and when I try to
restart the server it does not work.

So I tried to force the disconnection of customers before closing the
server (at the connection I store client in a collection), the
customer logs out fine but when I restart the server, I get an error
on bind ( or ENXIO No such device or address).

I should mention that this error occurs only on Linux, the same code
works on Windows without problem.

Thank you in advance

Chubb

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Marc · 2010-05-13 13:55

without simple sample code it is hard to tell whats going wrong.

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theo · 2010-05-13 17:02

Just a wild guess: Synapse has a property EnableReuse(Value: Boolean);
http://synapse.ararat.cz/doc/help/blcksock.TBlockSocket.html#EnableReu
se

From http://linux.die.net/man/7/socket
QuoteLinux will only allow port re-use with the SO_REUSEADDR option
when this option was set both in the previous program that performed a
bind() to the port and in the program that wants to re-use the port.
This differs from some implementations (e.g., FreeBSD) where only the
later program needs to set the SO_REUSEADDR option. Typically this
difference is invisible, since, for example, a server program is
designed to always set this option.

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chubb · 2010-05-17 03:59

Welcome

Thank you theo, after some research using the links provided, I
discovered that there is a parameter 'SO_REUSEADDR' to specify that we
can reuse the socket immediately

Below is a part from the forum
(http://linuxfr.org/forums/27/18820.html)

QuoteThe TCP RFC describing states that after closing a socket, it
must remain "useless" for a certain time (typically the maximum round-
trip time set for a TCP connection), only to avoid reopening the same
ports, it recovers bits of the previous connection packets that were
in transit through the maze of the Internet.

After completing a socket, looks with "netstat-ap - ip" the list of
existing sockets in the system: those that are closed are in such a
state of "TIME_WAIT".
Thank you everybody

Good day