Description. Make sure telnet and nc tools are installed on the Linux server you are trying to test connectivity. Telnet can be used to test tcp port connections, where as nc can be used to test both tcp/udp ports connectivity. Telnet and nc are common tools used to test port connectivity from Linux server. 测试TCP和UDP端口的方法下面以Linux平台为例，讲述测试TCP和UDP端口的方法。有两个命令可以用来测试端口，一个是telnet，一个是nc，但telnet只能用于测试TCP端口，而nc即可用于测试TCP端口也可用来测试UDP端口。【telnet命令的用法】telnetIPport例如：[root@localhost]#telnet192.168.0. You've opened a UDP port on your server but not sure how to check if you can reach it from the outside. Telnet is both a protocol allowing us to access a remote device to control it and the program used to connect through this protocol. You then go on with something else (or just wait doing nothing) until (or if) the remote process sends some packets back. It begins in command mode, where it prints a telnet command prompt ("telnet>").. The standard telnet utilities that ship with linux or windows allow to telnet to services running on TCP ports. UDP on the other hand doesn't really fit the telnet model - its more of a fire-and-forget system where you fire-off a series of packets towards the destination. If telnet is invoked with a host argument, it performs an open command implicitly. telnet – telnet command is used for interactive communication with another host using the TELNET protocol. It begins in command mode, where it prints a telnet command prompt (“telnet>”). When testing TCP ports, you can check with tools like nmap or nc only from the outside, but the nature of UDP is that it doesn't send anything back so you need to monitor the port on the receiving server to see if you receive any packets from the remote server.
The telnet program, which is not the Telnet protocol, can be useful to test port states which is the functionality this tutorial …
Probar puertos UDP con telnet en Linux Publicado por Oscar Meza en 17 julio, 2018 17 julio, 2018 Ya sabes lo fácil que es probar puertos TCP con telnet, pero para probar puertos UDP no utilizamos telnet si no que en su lugar usamos la herramienta netcat de la siguiente forma. However the utility netcat can be used for working with udp ports in a very similar manner to default telnet utility. The Telnet protocol is the “cheap” version of ssh, unencrypted, vulnerable to sniffing and Man In the Middle attacks, by default the Telnet port must be closed. The telnet command is used for interactive communication with another host using the TELNET protocol. They do not support udp ports.