This chapter contains the following recipes:
The goal of Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) is to pass information between end applications, for example, from a web client to a web server, mail client to a mail server, and so on. This is done by providing identification to end applications and forwarding packets between them. These identifications are called port numbers, and a port number with its IP address is called a socket. In the following diagram you can see what happens when you open a connection from your browser to a web server. The web server listens on port 80 and you will open a connection, for example, from port 1024.
So, the server is listening to requests on port 80 and will send responses to you on port 1024.
While TCP is a reliable, connection-oriented protocol, UDP does not support connectivity and reliability, but simply transfers datagrams between two end processes.
In this chapter, we will focus on TCP, its behavior, various problems, and how to use Wireshark in order to isolate and solve them.
3.16.137.108