mail tcp ports

One, what is the port. Before we start talking about ports, let's talk about what port is. Often heard on the network "My host opened a number of port, will not be invaded AH." "or" it would be safer to open that port. Again, my service should

Hadoop-definitions of Computer Network PortsPort Introduction The ports described in this article are all logical ports, which refer to the ports in the TCP/IP protocol. The port number ranges from 0 to 65535, for example, port 80 used to browse Web

1024 The following is reserved for the system, and from 1024-65535 is used by the userFor personal writing applications, try not to use a port number between 0 and 1024.1024 to 65535 we can program with. This is not a Linux rule, it is the socket

Windows has many open ports. When you access the Internet, network viruses and hackers can connect to your computer through these ports. To change your system to a copper wall, you should close these ports, mainly including TCP 135, 139, 445, 593,

e-mail protocol has SMTP, POP2, POP3, IMAP4, etc., are subordinate to the TCP/IP protocol cluster, by default, the connection is established through TCP ports 25, 110 and 143 respectively. For different purposes and functions, we will adjust the

Port concept: in network technology, Port has two meanings: one is physical Port, for example, ADSL Modem, Hub, switch, router is used to connect interfaces of other network equipment, such as RJ-45 port, SC port and so on. The second is the logical

In network technology, port has two meanings: one is physical port, for example, ADSL modem, Hub, switch, router is used to connect other network equipment interface, such as RJ-45 port, SC port and so on. The second is the logical port, which

How Linux firewalls Open specific portsIptables is a firewall under Linux and is also the service name.Service iptables Status View firewall stateService iptables start to turn on the firewallService iptables Stop shutting down the firewallService

OSI Reference ModelOSI RM: Open Systems Interconnect Reference Model (open Systeminterconnection Reference Model)The OSI Reference model has the following advantages: Simplifies the related network operation; Provide

1. Port 21:Port Description: port 21 is mainly used for FTP (File Transfer Protocol) services. Suggestion: Some FTP servers can be used by hackers to log on anonymously. In addition, port 21 will be used by some Trojans, such as Blade Runner, FTP