RFC 900，https://datatracker.ietf.org/doc/html/rfc900
```
Decimal Keyword Description References
------- ------- ----------- ----------
0 Reserved [JBP]
1-4 Unassigned [JBP]
5 RJE Remote Job Entry [13,32,JBP]
7 ECHO Echo [61,JBP]
9 DISCARD Discard [60,JBP]
11 USERS Active Users [56,JBP]
13 DAYTIME Daytime [59,JBP]
15 NETSTAT Who is up or NETSTAT [JBP]
17 QUOTE Quote of the Day [66,JBP]
19 CHARGEN Character Generator [58,JBP]
20 FTP File Transfer [Default Data] [31,62,JBP]
21 FTP File Transfer [Control] [31,62,JBP]
23 TELNET Telnet [78,JBP]
25 SMTP Simple Mail Transfer [31,68,JBP]
27 NSW User System FE [18,RHT]
29 MSG ICP [54,RHT]
31 MSG Authentication [54,RHT]
33 Unassigned [JBP]
35 Any Printer Server [JBP]
37 TIME Time [74,JBP]
39 RLP Resource Location Protocol [1,MA]
41 GRAPHICS Graphics [32,90,JBP]
42 NAMESERVER Host Name Server [31,65,JBP]
43 NICNAME Who Is [31,39,JAKE]
44 MPM FLAGS Protocol [JBP]
45 MPM Message Processing Module [recv] [64,JBP]
46 MPM MPM [default send] [64,JBP]
47 NI FTP [94,SK]
Reynolds & Postel [Page 13]
Assigned Numbers RFC 900
Port Numbers
49 Login Host Protocol [PXD]
51 IMP Logical Address Maintenance [50,AGM]
53 DOMAIN Domain Name Server [PM1]
55 ISI Graphics Language [10,RB6]
57 Any Private Terminal Access [JBP]
59 Any Private File Service [JBP]
61 NI MAIL [8,SK]
63 VIA Systems - FTP [DXD]
65 Unassigned [JBP]
67 Unassigned [JBP]
69 TFTP Trivial File Transfer [31,87,KRS]
71 NETRJS Remote Job Service [12,32,RTB]
72 NETRJS Remote Job Service [12,32,RTB]
73 NETRJS Remote Job Service [12,32,RTB]
74 NETRJS Remote Job Service [12,32,RTB]
75 Any Private Dial Out Service [JBP]
77 Any Private RJE Service [JBP]
79 FINGER Finger [32,37,KLH]
81 HOSTS2 Name Server [EAK1]
83 MIT ML Device [DPR]
85 MIT ML Device [DPR]
87 Any Private Terminal Link [JBP]
89 SU/MIT Telnet Gateway [MRC]
91 MIT Dover Spooler [EBM]
93 Device Control Protocol [DCT]
95 SUPDUP SUPDUP [21,MRC]
97 Unassigned [JBP]
99 Metagram Relay [GEOF]
101 HOSTNAME NIC Host Name Server [31,38,JAKE]
103 Unassigned [JBP]
105 CSNET-NS Mailbox Name Nameserver [88,MHS1]
107 RTELNET Remote Telnet Service [67,JBP]
109 POP Post Office Protocol [JBP]
110-129 Unassigned [JBP]
131 Unassigned [JBP]
132-223 Reserved [JBP]
224-241 Unassigned [JBP]
243 Survey Measurement [9,AV]
245 LINK [14,RDB2]
247-255 Unassigned [JBP]<i>
```
