After long days I am writing this article and this is the
complete package of these all articles about file transfer from one computer to
another. Till now I have shown how to transfer file from client to server or
server to client. But now I am merging these two things and creating one single
application which can send data/file from one client to another client. It
seems data is going directly from one client to another but actually it’s
rotating via Server, I will explain here these things.
I am planning to stop this article series on Socket
Programming in Desktop using C#.Net here for now and ignoring large file
transfer sample from client to client because now a day is era of Web
Programming. Long ago I tried to write code in web application with socket but
I failed because web and desktop is totally different type of architecture.
But in HTML5 is very powerful and it has introduced new
thing to develop socket programming on web as well. In HTML5 there has Web
Socket and using Web Socket Micorsoft has created SignalR which will be my next
attraction of discussion. I shall try to explain and shall create multiple
applications including Web Chat, message broadcasting system using these
technologies.
Before going to discuss Client to Client application I
would like to recap earlier two post:
I am trying to explain how these were working.
File Transfer from Client to Server
Server
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Client
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1. Server creates an IP End Point and a socket object
then bind socket object with IP end point and sends it to listen mode for
incoming client request.
5. Server
receive client request and accept it. Once connection established, server
create another socket object which will handle this client all requests until
connection ends. Client will be informed internally by TCP about connect success.
6. Start preparations
to store incoming byte data from client.
8. Server receives file byte data along with file name
and stores it in byte array.
9. Server retrieve file name from byte data.
10. Server opens a binary stream writer with file name
to store byte data in it.
11. Once file save complete server closes binary stream
writer and server socket objects.
14 Server program ends here.
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2. Client creates an IP End Point and a socket object.
3. Prepare byte data from file
which will be sent to server.
4. Try to connect to
server using client socket by help of IP end point.
7. Client starts sending
byte data over connected socket.
12. Once data transfer
complete and server closes socket connection, client also close client socket
object.
13. Client program work ends
here.
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File Transfer from Client to Server
Server
|
Client
|
1. Server creates an IP End Point and a socket object
then bind socket object with IP end point and sends it to listen mode for
incoming client request.
4. Server
receive client request and accept it. Once connection established, server
create another socket object which will handle this client all requests until
connection ends. Client will be informed internally by TCP about connect success.
6.
Prepare
byte data from file which will be sent to client.
7. Server starts sending
byte data over connected socket.
12. Once data transfer
complete and client closes socket connection, server also close server socket
object.
13. Server program work ends here.
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2. Client creates an IP End Point and a socket object.
3. Try to connect to server using client socket by help
of IP end point.
5. Start preparations
to store incoming byte data from server.
8. Client receives file byte data along with file name
and stores it in byte array.
9. Client retrieve file name from byte data.
10. Client opens a binary stream writer with file name
to store byte data in it.
11. Once file save complete client closes binary stream
writer and server socket objects.
14. Client program work ends here.
|
So from these two tables it’s
clear that in (1) Client to Server data transfer and (2) Server to Client
program server and client is doing just like opposite execution.
When we transfer file over
internet one client cannot connect to another directly because maximum client
do not use static/global IP, so they cannot reach over other internet location
directly. So to transfer file from client to client need server help. Server
stays internet with a static IP which is accessible globally. We will use server as temporary storage and to
connect other client via server. Overall architecture will be as below:
In above picture, Client A
is trying to send file to client B and both are taking help of Server in between
to make connection. Client A and B both are inaccessible from outside internet
because these are may be in DHCP inside a LAN or its IP has generated by some
other local router. So both will connect to server and transfer data.
Now follow below
communication chart to understand how data will be transferred. This chart is
combination of first two chart.
Data Transfer -- > -------------->-----------------------> -------------->----------------------->
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Client A
|
Server
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Client
B
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2. Client-A create IP End Point and a socket object.
4. Client A Prepare byte
data from file which will be sent to server.
5. Client A tries to
connect server using client socket by help of IP end point.
8. Connection established with client A and server.
11. Client A starts
sending byte data over connected socket.
20. Client A receive file transfer success message from
server.
22. Socket object closes and dispose.
24. Client A process ends here.
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1. Server creates an IP End Point and a socket object
then bind socket object with IP end point and sends it to listen mode for
incoming client request.
7. Server
receives two client requests and accept these. Once connection established,
server create new socket object for each connection (here total two, suppose
sockObjectA for Client A and sockObjectB for Client B). These will handle client’s
all requests until connection ends. Client will be informed internally by TCP
about connect success. In our case sockObjectA will receive data and sockObjectB
will send data.
For real
life application can use socket object list (say array list or hash table)
with some hash table to track client name and socket object name.
10. Start preparations
to store incoming byte data from client A through sockObjectA.
12. Server receives file byte data along with file name
and stores it in byte array. For large file can store in temporary file but I
would suggest to store in array for faster processing.
13. Server starts sending byte data over connected
socket sockObjectB to client B.
19. Server receive EOF successful message from client B
and pass information to client A about file transfer success.
21. Server initiate to disconnect socket connection for
sockObjectA and sockObjectB, so connection break with server and client A and
B.
26. Server process ends here for my case. For real life
project server will stay in listen mode for next client request.
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3. Client B creates IP End Point and a socket object.
6. Client B tries to connect server using client socket
by help of IP end point.
9. Connection established with client A and server.
14. Client B receives file byte data along with file
name and stores it in byte array.
15. Client retrieve file name from received byte data.
16. Client opens a binary stream writer with file name
to store byte data in it.
17. Once file save complete client (do some technique
to understand End Of File - EOF) closes binary stream writer and server
socket objects.
18. Send a message to server to inform client A about
file transfer success.
23. Socket object closes and dispose.
25. Client B process here.
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If you send large file then logic will be same and you
need to loop step 11 to 20 until file ends. Here I have used EOF and then can
use some fixed data packet every time. So once each packet receive in Client
B, it will inform that successful receive of packet number and ask server to
send next packet.
For large file server will store file temporarily
because connection speed in client A and B may not be same. Client A can send
much faster data but client B may get it very slow. So buffering concept need
to implement in server.
If possible I shall write this code in future.
Now I am posting this logic next will write code and
once finish will post it for you with downloadable source code.
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