How to understand the source and destination ports of tcp? The source port number in TCP is where your packet comes from, and the destination port number is where your packet is going. Remember that the source and destination port numbers are not necessarily the same. For example, if you visit a web page, your destination port number must be 80 and the source port number must be a random port greater than 1024. Anyway, no matter what service you want, the destination port number is the same, and the source port and the destination port randomly choose a port of 1024 to form a connection with this destination port. Tcpudp is a kind of cooperative TCP similar to registered mail. Udp is similar to telegraph. You don't need to know if the other party has received it. The use of emule is very simple. Look at the interface before you think. Generally speaking, the port number of windows is an unsigned integer, that is, all numbers in the system starting from 065535 are separated from TCP, that is, the port number occupied by UDP can start from 065535TCP or start from 065535, and they are independent. For example, one program can use TCP to occupy port 2000, and another program can use UDP to occupy port 2000 without interference.