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0. content

1. some useful port numbers
2. check services with telnet
3. check mail services / accounts on ports: 25 (smtp), 110 (pop3), 143 (imap4)
4. WHOIS records (WHO IS the owner of the domain xxx.com)
5. DNS service (port: 53)

1. some useful port numbers

Some important port numbers: echo 7; daytime 13; ftp 20/21; telnet 23; time 37; http 80; loc-srv 135; netbios 137udp / 138udp / 139tcp, https 443, lotusnote 1352, pcanywheredata 5631, snmp 161/162.

What are the offical SSL ports?

    nsiiops      261/tcp   # IIOP Name Service over TLS/SSL
    https        443/tcp   # http protocol over TLS/SSL
    smtps        465/tcp   # smtp protocol over TLS/SSL (was ssmtp)
    nntps        563/tcp   # nntp protocol over TLS/SSL (was snntp)
    imap4-ssl    585/tcp   # IMAP4+SSL (use 993 instead)
    sshell       614/tcp   # SSLshell
    ldaps        636/tcp   # ldap protocol over TLS/SSL (was sldap)
    ftps-data    989/tcp   # ftp protocol, data, over TLS/SSL
    ftps         990/tcp   # ftp protocol, control, over TLS/SSL
    telnets      992/tcp   # telnet protocol over TLS/SSL
    imaps        993/tcp   # imap4 protocol over TLS/SSL
    ircs         994/tcp   # irc protocol over TLS/SSL
    pop3s        995/tcp   # pop3 protocol over TLS/SSL (was spop3)
    msft-gc-ssl  3269/tcp  # Microsoft Global Catalog with LDAP/SSL

2. check services with telnet

To check e.g. an SMTP mail server, just open a terminal (telnet.exe under Windows NT/2000/XP) and connect to the port 25 of your mail server.

On Linux / UNIX type:

If the connection is avilable you should see something like that it the server is a Microsoft Exchange Server:

or the follwing on a unix mail host with sendmail:

Use the follwing link the see a real example: telnet://mail.centralnet.ch:25 or directly with the IP-Address: telnet://193.135.146.10:25

Note

This kind of link may (?) not run on a Windows 95/98 Computer because of missing telnet software (try hyper terminal). Anyway it works fine with WinNT/2000/XP and all kind of Linuxes / UNIXes.

You can use the syntax from above to create links with your own servers. You'll find a list of well known port numbers above. I have created a long list of such links on a "Site Check" page to quickly access routers and service.

Check out my Small Network Troubleshooting Guide: SmallNetworkTroubleshooterWin2k.htm

3. check mail services / accounts on ports: 25 (smtp), 110 (pop3), 143 (imap4)

NOTE: If you need more than the follwoing commands, read the RFC2821.
All RFC's are here: http://freesoft.org/CIE/search.htm.

If you have a connection with an smpt server, you can send a mail from there without any dedicated mail program:

1. Connect to a mail server: telnet://mail.centralnet.ch:25
2. Type in the command "help" (if you can't see what you type, you have to enable local echo in your terminal program)
   You should get a list of avilabel commands on most servers.
3. Type in "mail from:myname@domain.ch" and replace the italic words with the correspondings. (you can not )
   You should get an OK. if the syntax is correct.
4. Type in "rcpt to:rcpt@domain.ch" where the italic words are the destination address for the mail.
   You should get another OK. if the syntax is correct.
5. Type in "data"
   You should get another OK. if the syntax is correct.
6. Now you can type the e-mail text. To end it hit return type a point "." and hit return again.
   You get a confirmation that the server will deliver the mail.
7. Type in "quit" to close the connection.

To check a POP3-Account use the following commands after connect: (e.g. RFC1939, std53)
user username --> pass password --> list --> top mailnr amountOfLines --> retr mailnr -->dele mailnr -->quit

To check an IMAP4-Account use the following commands after connect:
a001 LOGIN username password --> return --> A001 LOGOUT --> return

To check a web server's basic functionality:

1. Connect to port 80 of the server: e.g. telnet://www.sbb.ch:80
2. Type "get index.html" and hit return.
   If the service is alive, you'll get at least an error message.

4. WHOIS records (WHO IS the owner of the domain xxx.com)

You can search for a name of a domain owner or the domain name itself. If the domain is activ, you get the primary and secondary DNS server IP-address, so you can use the DNS-check tool below to find out, what the official hosts of the domain are.

WHOIS for any .ch or .li domain
WHOIS for any generic domains such as .com .org ...

WHOIS for European IP addresses: http://www.ripe.net/db/whois/whois.html
WHOIS for American IP addresses (ARIN): http://www.arin.net/whois/index.html
WHOIS for Asia-Pacific IP addresses (APNIC): http://www.apnic.net/apnic-bin/whois.pl 
Info about Swiss Registries: http://www.ripe.net/ripencc/mem-services/general/indices/CH.html 
(Details here: http://www.ripe.net/ripencc/about/regional/)

5. DNS service (port: 53)

With the DNS check tool, you can find out if your DNS server is configured properly. If you don't know the DNS of a domain have look at chapter WHOIS records.
Furthermore this tool will show you all registered hosts and especially the mail-host(s) for a domain - the MX-record.

The result mustn't have an error; warnings are normal.

DNS CHECK tool for any domain and any DNS (from IP-Plus)
http://freesoft.org/CIE/Course/Section2/13.htm  

e.g. DNS CHECK FOR  centralnet.ch  BY   ns.centralnet.ch (secondary DNS)
e.g. DNS CHECK FOR  centralnet.ch  BY  193.135.146.10 (secondary DNS)

You can find a list of useful tool under: http://www.dns.net/dnsrd/

Created and copyright by Raphael Müller, Last Update: 22. January 2004