I want to write a tcp server and client application, which has several different connections to each other where the client uses the same port number.
So far I understand it, the server has a listener port and when the client calls it, then I get a new socket for this new connection on the server side, when I call
accept();
Right? So on Server side I can identify my connection with this new socket and send data through it.
Now my understanding problem with the client side. There I get my socket when I call
socket(AF_INET, SOCK_STREAM, 0)
so I have only one socket. In the
connect()
I can specify remote adress and so on. So when I understand it correctly I can use one socket to make several connects to different adresses/port pairs to create different connections. Right?
But how can I now see in the Client from which logical connection I receive my data or how can I send it when 2 logical connections use the same local port at the client? On serverside I have 2 sockets when I have 2 accept called but what about the client side? For send and receive I have only one socket handle?
Or do I have to call socket() for each logical connection on the client?
So when I understand it correctly I can use one socket to make several connects to different adresses/port pairs to create different connections. Right?
No. A TCP socket can only be used once. When its connection has finished, or even if connect() just fails to make a connection, you must close the socket and create a new one if you want to make a new connection.
But how can I now see in the Client from which logical connection I receive my data or how can I send it when 2 logical connections use the same local port at the client?
Every TCP connection will have its own unique socket allocated for it. It is your responsibility to keep track of them.
On serverside I have 2 sockets when I have 2 accept called but what about the client side?
The exact same thing happens on the client side, too. You need to create and connect a separate socket for every TCP connection you make. So, you will have a new pair of socket()/connect() calls for every connection.
For send and receive I have only one socket handle?
No, you will have a separate socket for each connection, just like on the server side.
Or do I have to call socket() for each logical connection on the client?
Yes, and connect(), too.