Does the Listening socket with the socket used by the newly created use the same port?

Question

0.00/5 (No votes)

See more:

I think they are using different ports.But when I find some information in the Internet,it show that they are using the same port.Can anyone tell why?Thank you.

For example:
My server machine listen port is 5555, when a client A to connect, the server creates a socket (port by means upstairs to 5555) to communicate, are there a port can be used in two places?
Subsequently, the client B to connect to the server and create a socket (port means in accordance with the upstairs is 5555) to communicate the same server with the emergence of three 5555 ports, Is this correct?

Posted 14-Dec-11 23:33pm

PEIYANGXINQU

Updated 15-Dec-11 0:41am

Richard MacCutchan

v3

Add a Solution

2 solutions

Solution 2

The server listens on the fixed port, and when a client connects it will redirect that connection to a dynamically created port. The client and server will now communicate through the sockets on the dynamic port, while the server continues to listen on the fixed port for other connection requests.

Posted 15-Dec-11 0:44am

Richard MacCutchan

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Mike O'Neill · Accepted Answer · 2011-12-16T12:13:00

Richard - I think that's incorrect.

Each connection is identified uniquely, and distinct from all other connections on the Internet, using a 4-tuple comprising: IP of the server, port of the server, IP of the client, port of the client.

Since each different client connection will have a different IP and/or a different port, it's perfectly OK that the server uses the exact same numbers for IP and port for all of its clients. And that's exactly what happens.

The exact sequence (on the server side) is when a new connection is accepted (using a call to accept()), a new socket is created in the server. On the server side (i.e., the local side), the new socket has the same IP and port as all other sockets created by the server. On the remote side, however, the new socket has the IP and port of the client, thus differentiating the connection from all other connections to the server.

You might have heard of the term "ephemeral ports", which refers to the automatic selection of a new port number for each new outgoing connection. This concept is a client-side concept, not a server-side concept, and applies only to outgoing connections, not to incoming connections.

Mike