say i am using tcp protocol and i receive a data packet.my doubt is how will this packet be directed to its appropriate proccess.
Packets are directed to the correct process by the Protocol (IPv4) or Next Header (IPv6) field. For example, TCP is protocol 6, so the packet payload of a packet with 6 as the protocol number would be sent to the TCP process. If the protocol number is 17, then the payload of the packet is sent to the UDP process, etc. IANA maintains the Protocol Numbers page.
i have heard tcp uses port number so the process which is using current port number is given the data packet.
I think you are confusing the network layers. Packets are IP datagrams. TCP datagrams are segments because TCP segments a data stream. An application will register with TCP to get a port number, and that application has exclusive use of the port number until it releases it.
but what if more than one process is using the same port number.i heard this is not possible i.e different process using same port number but what if i am using youtube from different windows of chrome and edge .all has to go to the same ip and same port number how will the incoming packet distinguish which process it goes to.
A TCP port number is assigned to a single process. Your example would be incorrect because a browser will use ephemeral port numbers, where it lets TCP assign a random port number from the ephemeral range for the OS on which it is running. In fact, browsers will open multiple connections to the web server, each using a different source port number. It is the server side that must listen on a well-known port number.
Remember that port numbers are per protocol; TCP port 12345 is not UDP port 12345. Also, not all transport protocols use port numbers. Some use something else, and some use nothing because they are tied to a single application.
so i am writing a client-server program using berkeley sockets.so the client uses some port number generated by the brekeley socket api,and server can distinguish two different clients on the same machine.
Your server will need to listen on a specific TCP port number so that clients know how to reach it. The clients will use port
0, which is reserved, and TCP will then assign a random source port number from its ephemeral range. The server will get the client port number from the TCP segment, and it will reply to that port number. The TCP connection is identified by both the source and destination IP addresses and TCP port numbers.