Socket TCP questiuon.

  • Thread starter Thread starter Anders Both
  • Start date Start date
A

Anders Both

If you send data using TCP and Socket, can the client then be 100% sure that
if it send´s data and no exception uccur, then the data will also arrived in
a a correct way on the server.

What if e.g. some router on the way has restarted or if it restarts just in
the same time as the data is beeing send.

?
 
Hi Anders!

If you send data using TCP and Socket, can the client then be 100% sure that
if it send´s data and no exception uccur, then the data will also arrived in
a a correct way on the server.
Click to expand...
What if e.g. some router on the way has restarted or if it restarts just in
the same time as the data is beeing send.
Click to expand...

If you use UDP, then your application must handle these things.
If you use TCP, then the System itself is doing the whole work for you.
(e.g. sending parts of your data in packages, waiting for an
acknowkledge-message, resending data if a packet is lost ...

If everything clear now, or do you need more details? Or do you have a
concrete problem that should be solved?

With kind regards,

Konrad
 
I am back already.

But what if you have a socket connection between a client and a server. And
the server sometimes send´s some data to the client, like lets say every 5
minute, and the client is just waiting to reseive this data. What if the
server frezzes or if the connection is lost in some way, how (if it is
alerted) will the client then be allerted when using asynchronous Sockets
(TCP).

Best Regards Anders Both
 
Hi Anders!

But what if you have a socket connection between a client and a server. And
the server sometimes send´s some data to the client, like lets say every 5
minute, and the client is just waiting to reseive this data.
Click to expand...
I think, that it is recommend to send some dummy stuff like "pings"
through this connection. (Or this is the way, I am going on -> server
side <- to be sure, that all clients are still alive ...
What if the
server frezzes or if the connection is lost in some way, how (if it is
alerted) will the client then be allerted when using asynchronous Sockets
(TCP).
Click to expand...

I haven't tested this stuff until now. If the server didn't respond,
because simply a thread is locked, then you will not recognize it. But
the connection should be closed, if the server crashes or there will be
a network problem for some time ... But as I told you: I am not that
sure - You had to test that a little first!

If you need multiple clients to connect to a server and simply get some
information every 5 mins: Ever thought about remoting? Then all you have
to do is calling a function in an Remote Object .... That could be much
better and much easier than building a tcp/ip solution on your own.

With kind regards,

Konrad
 
Thx,

I can not use remoting, because the connection has to be from a java client
on a web-page to a c# service.

But I will find out everything.

Thx alot.
 
Thx,

I can not use remoting, because the connection has to be from a java
client on a web-page to a c# service.

But I will find out everything.

Thx alot.
Click to expand...

Anders,

You may have already found an answer for this, if not, hopefully this
helps.


The only way the client can know that the connection is gone, is if the
connection is closed by the server, or the client tries to send a data
packet, but hits its timeout period on the send method.

If the connection is lost, for example a router dies, then the only way to
know the connection is gone, is from a timeout, as you will never get the
shutdown (fin) message from the socket that initiated the shutdown/close.

You have two simple options that I can think of off the top of my head.

You can make the clients repond to the servers data, and have the
SendTimeout option set on the client sockets.
Below is from the MSDN help.

// Send operations will time-out if confirmation
// is not received within 1000 milliseconds.
s.SetSocketOption (SocketOptionLevel.Socket, SocketOptionName.SendTimeout,
1000);


Your other options is if the server is known to always send data at a
specific interval, then you can use a timer to watch for a missed packet.
Or you can send Keep-Alive messages every 10 seconds, if the data is not
regular enough, or you don't want the sockets locked for longer than
necessary with a lost connection.

So if the server sends "Alive" every 5 seconds, then set a timer's timeout
period to 10 seconds. Whenever any data arrives on the socket, reset the
timer. If the timers Elapsed event is raised, then you know the server is
possibly not responding.

For more detail on Socket programming for C#, you can not go past Richard
Blum's book "C# Network Programming" - published by Sybex.


Scott Gaitskell
 
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