Common Network Port Numbers Flashcards: Protocols, TCP/UDP & Uses
Study 88 cards on common network ports, TCP/UDP transports, service uses, port ranges, and practical protocol distinctions.
Bu deste hakkında
Build a practical map of common network service ports with 88 independently authored cards. Twelve foundation and distinction cards cover port roles, IANA ranges, independent TCP and UDP namespaces, assignment limits, conventional versus configured ports, client source ports, DNS transport behavior, DHCP endpoints, FTP channels, and common implicit-TLS pairs.
The remaining 76 cards practice 38 mappings in both useful directions: service → conventional or registered port, transport, and concise use; and port/transport → service and concise use. Coverage includes FTP control and active-mode data, SSH/SFTP, Telnet, SMTP relay, DNS, DHCPv4 server and client endpoints, TFTP, HTTP, Kerberos, POP3, NTP, the three NetBIOS services, IMAP, SNMP queries and notifications, BGP, LDAP, HTTPS including HTTP/3, direct-hosted SMB, IKE, syslog, SMTP submission, LDAPS, IMAPS, POP3S, Microsoft SQL Server, L2TP, PPTP, RADIUS authentication, MySQL, RDP, IPsec NAT Traversal, SIP, and PostgreSQL.
This is a focused recall deck, not a copy of the full IANA registry. It excludes exhaustive assignments, port-scanning or attack instructions, firewall policy, every vendor-specific alternate, dynamic service-discovery inventories, and the claim that a port number proves which application produced observed traffic. Registered, default, conventional, and common-use wording stays explicit because services can be reconfigured or negotiated elsewhere.
The sequence establishes the port model first, then mixes web, email, infrastructure, remote-access, file-transfer, network-management, directory, VPN, voice, Windows, and database families. Opposite directions for the same mapping stay at least 38 intervening cards apart. Near-duplicate DNS, DHCP, FTP, SNMP, NetBIOS, and IPsec cues keep at least three unrelated cards between them, and the TLS-pair distinction stays at least three unrelated cards from its closest overlapping mapping. The review scheduler handles continued spacing after installation.
Open Study Contributor independently authored the prompts, answers, mapping choices, organization, metadata, and cover from common networking knowledge checked against the current IANA Service Name and Transport Protocol Port Number Registry, relevant RFCs, and official vendor documentation. Organization and product names identify protocols, services, or sources only; no affiliation or endorsement is claimed. No competitor card text, certification questions, answer keys, course text, or source prose was copied.
The CC0 label applies to the original prompts, answers, organization, metadata, and generated cover to the extent applicable rights exist. It does not claim ownership of protocol facts, standards, organization names, product names, or third-party source material.
Bu destedeki kartlar
Kart 1
Soru
What does a transport-layer port number identify?
Cevap
An application endpoint within a host for one transport protocol. The IP addresses, transport protocol, and source and destination ports together identify a communication flow.
Kart 2
Soru
Are TCP port 53 and UDP port 53 the same port?
Cevap
No. TCP and UDP have independent 16-bit port namespaces, so 53/TCP and 53/UDP are separate transport endpoints.
Kart 3
Soru
What is the IANA System Port range?
Cevap
0–1023. These are also called Well-Known Ports and are assigned by IANA under the stricter System Port procedures.
Kart 4
Soru
What is the IANA User Port range?
Cevap
1024–49151. These are also called Registered Ports and may be assigned by IANA to services.
Kart 5
Soru
What is the IANA Dynamic or Private Port range?
Cevap
49152–65535. IANA does not assign ports in this range; systems commonly use it for temporary or private endpoints.
Kart 6
Soru
Does an IANA port assignment prove what observed traffic is—or that it is safe?
Cevap
No. A registration is a naming convention, not traffic identification, authorization, or a security verdict. Verify the actual protocol and context.
Kart 7
Soru
Must a service use its registered or conventional port?
Cevap
No. Administrators and applications can choose another port, negotiate one dynamically, or discover it through mechanisms such as DNS SRV records.
Kart 8
Soru
What port roles are typical in a client-server connection?
Cevap
The server usually listens on a known destination port, while the client uses a temporary source port. Either side can be configured differently.
Kart 9
Soru
SSH and SFTP — common server port and transport?
Cevap
TCP 22. SSH provides encrypted remote access, and SFTP normally runs as a subsystem inside the same SSH connection.
Kart 10
Soru
53/UDP or 53/TCP — which service?
Cevap
DNS. Routine queries often use UDP, while full DNS implementations also support TCP; zone transfers use TCP.
Kart 11
Soru
SMTP relay between mail servers — common port and transport?
Cevap
TCP 25. SMTP uses it for server-to-server mail transfer; user mail submission normally uses port 587 or implicit TLS on 465.
Kart 12
Soru
HTTP without TLS — conventional port and transport?
Cevap
TCP 80 for conventional HTTP/1.1 and HTTP/2 connections. The service can be configured on another port.
Kart 13
Soru
67/UDP — which DHCPv4 endpoint?
Cevap
The DHCPv4 server endpoint. Clients send server-directed DHCP messages to UDP port 67.
Kart 14
Soru
21/TCP — which service and channel?
Cevap
FTP control. It carries commands and replies; file data uses a separate connection.
Kart 15
Soru
SNMP requests and responses — common agent port and transport?
Cevap
UDP 161. Managers commonly send queries to an SNMP agent there; other SNMP transports exist.
Kart 16
Soru
1433/TCP — which database service?
Cevap
Microsoft SQL Server's default instance. TCP 1433 is the default Database Engine port, but named or custom instances may use another port.
Kart 17
Soru
23/TCP — which remote-access protocol?
Cevap
Telnet. It provides a plaintext remote terminal session and does not protect credentials or traffic with encryption.
Kart 18
Soru
NTP — usual port and transport?
Cevap
UDP 123. NTP normally uses UDP for time synchronization; IANA also has a TCP 123 registration, but that is not the usual NTP transport.
Kart 19
Soru
Why must a general-purpose DNS implementation support both UDP and TCP?
Cevap
UDP handles most routine queries efficiently, while TCP handles cases such as zone transfers and responses that do not fit the chosen UDP path. Both use port 53.
Kart 20
Soru
POP3 — conventional port and transport?
Cevap
TCP 110. POP3 retrieves mail; it can upgrade with STLS, while implicit TLS uses TCP 995.
Kart 21
Soru
443/TCP or 443/UDP — which web service?
Cevap
HTTPS. HTTP/1.1 and HTTP/2 normally use TLS over TCP 443; HTTP/3 uses QUIC over UDP 443.
Kart 22
Soru
DHCPv4 client endpoint — port and transport?
Cevap
UDP 68. Servers send client-directed DHCPv4 messages to port 68.
Kart 23
Soru
69/UDP — which file-transfer protocol?
Cevap
TFTP. A client sends the initial read or write request to UDP 69; the transfer then continues with a server-selected UDP transfer identifier.
Kart 24
Soru
162/UDP — which network-management traffic?
Cevap
SNMP notifications, traditionally called traps. Notification receivers commonly listen on UDP 162.
Kart 25
Soru
MySQL classic protocol — default port and transport?
Cevap
TCP 3306. It is the default for classic MySQL client-server connections and can be reconfigured.
Kart 26
Soru
How do FTP control, active-mode data, and passive-mode data ports differ?
Cevap
Control uses TCP 21. The server side of the default active-mode data connection uses TCP 20, while passive mode negotiates another server port.
Kart 27
Soru
3389/TCP or 3389/UDP — which remote-desktop service?
Cevap
Microsoft Remote Desktop Protocol (RDP). TCP and UDP 3389 are the standard defaults, and the listening port can be changed.
Kart 28
Soru
Syslog's conventional UDP transport — port?
Cevap
UDP 514. Classic syslog over UDP has no delivery guarantee; TCP 514 is registered to the shell service, not syslog.
Kart 29
Soru
How do DHCPv4 server and client ports pair up?
Cevap
UDP 67 is the server port, and UDP 68 is the client port. Client-to-server messages target 67; server-to-client messages target 68.
Kart 30
Soru
IMAP — conventional port and transport?
Cevap
TCP 143. IMAP accesses and manages mail on a server; implicit TLS uses TCP 993.
Kart 31
Soru
445/TCP — which file-sharing service?
Cevap
Direct-hosted SMB. Modern SMB servers commonly listen on TCP 445 without the older NetBIOS session layer.
Kart 32
Soru
88/UDP or 88/TCP — which authentication protocol?
Cevap
Kerberos. Clients and Key Distribution Centers support both transports; TCP also handles requests or replies too large for UDP.
Kart 33
Soru
FTP's default active-mode data connection — server-side port and transport?
Cevap
TCP 20. This is the server's default source port for active-mode data; passive FTP negotiates another server port.
Kart 34
Soru
BGP — standard operational port and transport?
Cevap
TCP 179. RFC 4271 defines BGP peer sessions over TCP; IANA separately retains a UDP 179 registry entry.
Kart 35
Soru
5432/TCP — which database service?
Cevap
PostgreSQL. TCP 5432 is the customary default server port, but an installation can choose another port.
Kart 36
Soru
IKE for IPsec — initial port and transport?
Cevap
UDP 500. IKE normally begins there; NAT traversal commonly moves subsequent IKE and encapsulated ESP traffic to UDP 4500.
Kart 37
Soru
NetBIOS Name Service — common port and transport?
Cevap
UDP 137. It supports NetBIOS name registration and lookup; direct-hosted modern SMB does not require it.
Kart 38
Soru
587/TCP — which email role?
Cevap
SMTP message submission. Mail clients normally submit outgoing mail to a submission server there, often with STARTTLS; server relay remains on TCP 25.
Kart 39
Soru
389/TCP — which directory protocol?
Cevap
LDAP. Ordinary connection-oriented LDAP commonly uses TCP 389; IANA also registers UDP 389 for connectionless LDAP.
Kart 40
Soru
L2TP — common port and transport?
Cevap
UDP 1701. L2TP carries tunnel control and data but does not provide encryption by itself; deployments often pair it with IPsec.
Kart 41
Soru
138/UDP — which NetBIOS service?
Cevap
NetBIOS Datagram Service. It carries connectionless NetBIOS datagrams, historically used in NetBIOS over TCP/IP environments.
Kart 42
Soru
IMAPS — default port and transport?
Cevap
TCP 993. It starts IMAP with an immediate TLS handshake for encrypted mail access.
Kart 43
Soru
636/TCP — which directory-service convention?
Cevap
LDAPS, the commonly used implicit-TLS port for LDAP. LDAP can also negotiate TLS on TCP 389.
Kart 44
Soru
1723/TCP — which VPN control protocol?
Cevap
PPTP control. PPTP uses TCP 1723 for control, while tunneled PPP data travels in GRE—not on TCP or UDP port 47.
Kart 45
Soru
NetBIOS Session Service — common port and transport?
Cevap
TCP 139. It provides connection-oriented NetBIOS sessions and historically carried SMB before direct-hosted SMB on TCP 445.
Kart 46
Soru
995/TCP — which mail-access service?
Cevap
POP3S. It starts POP3 with an immediate TLS handshake for encrypted mail retrieval.
Kart 47
Soru
RADIUS authentication and authorization — standard port and transport?
Cevap
UDP 1812. RADIUS accounting normally uses the separate UDP port 1813.
Kart 48
Soru
IPsec NAT Traversal — port and transport?
Cevap
UDP 4500. It carries IKE and UDP-encapsulated ESP when NAT traversal is in use.
Kart 49
Soru
5060/UDP or 5060/TCP — which signaling protocol?
Cevap
SIP. It commonly uses UDP or TCP 5060 for session signaling; SIP over TLS conventionally uses TCP 5061.
Kart 50
Soru
Which common dedicated ports distinguish plaintext or STARTTLS-capable services from implicit-TLS variants?
Cevap
HTTP 80 ↔ HTTPS 443; IMAP 143 ↔ IMAPS 993; POP3 110 ↔ POP3S 995; LDAP 389 ↔ LDAPS 636. A port alone does not prove that TLS is configured correctly.
Kart 51
Soru
22/TCP — which secure remote-access service?
Cevap
SSH. It supports encrypted remote login, command execution, tunneling, and file-transfer tools such as SFTP.
Kart 52
Soru
DNS — registered port and required general-purpose transports?
Cevap
Port 53 over UDP and TCP. Most ordinary queries start with UDP, while TCP is required for full implementations and used for zone transfers and other larger exchanges.
Kart 53
Soru
25/TCP — which email function?
Cevap
SMTP mail relay and delivery between servers. End-user clients normally submit new mail on TCP 587 or TCP 465 instead.
Kart 54
Soru
80/TCP — which conventional web service?
Cevap
HTTP without TLS. It is the conventional port for HTTP/1.1 and HTTP/2, although servers can listen elsewhere.
Kart 55
Soru
DHCPv4 server endpoint — port and transport?
Cevap
UDP 67. DHCPv4 clients direct server-bound messages to that port.
Kart 56
Soru
FTP control — server port and transport?
Cevap
TCP 21. Commands and replies use the persistent control connection; data travels on a separate connection.
Kart 57
Soru
161/UDP — which network-management traffic?
Cevap
SNMP requests and responses. Managed agents commonly listen on UDP 161 for manager queries.
Kart 58
Soru
Microsoft SQL Server default instance — default port and transport?
Cevap
TCP 1433. Named instances may use dynamic or custom ports, with SQL Server Browser commonly using UDP 1434 for discovery.
Kart 59
Soru
Telnet — conventional port and transport?
Cevap
TCP 23. Telnet carries terminal traffic in plaintext, so SSH is the usual secure replacement.
Kart 60
Soru
123/UDP — which time service?
Cevap
NTP. Network Time Protocol commonly synchronizes clocks over UDP 123.
Kart 61
Soru
110/TCP — which mail-access protocol?
Cevap
POP3. It downloads or retrieves mail from a server; implicit TLS uses TCP 995.
Kart 62
Soru
HTTPS — common port and transports?
Cevap
Port 443: TCP for HTTP/1.1 and HTTP/2 over TLS, and UDP for HTTP/3 over QUIC.
Kart 63
Soru
68/UDP — which DHCPv4 endpoint?
Cevap
The DHCPv4 client endpoint. Servers direct client-bound DHCP messages to UDP 68.
Kart 64
Soru
TFTP — initial request port and transport?
Cevap
UDP 69. Only the initial request targets 69; the server chooses another UDP transfer identifier for the data exchange.
Kart 65
Soru
SNMP traps and other notifications — common receiver port and transport?
Cevap
UDP 162. SNMP notification receivers commonly listen there.
Kart 66
Soru
3306/TCP — which database protocol?
Cevap
The classic MySQL protocol. TCP 3306 is its default client-server port and is configurable.
Kart 67
Soru
RDP — standard port and transports?
Cevap
TCP and UDP 3389. Microsoft Remote Desktop uses them by default, though administrators can change the listening port.
Kart 68
Soru
514/UDP — which logging protocol?
Cevap
Syslog over UDP. It is a conventional lightweight transport without delivery guarantees; secure syslog commonly uses another transport and port.
Kart 69
Soru
143/TCP — which mail-access protocol?
Cevap
IMAP. It manages mail on the server; implicit TLS uses TCP 993.
Kart 70
Soru
Direct-hosted SMB — common server port and transport?
Cevap
TCP 445. It carries SMB directly over TCP without the legacy NetBIOS Session Service on TCP 139.
Kart 71
Soru
Kerberos KDC traffic — port and transports?
Cevap
UDP and TCP 88. Conforming clients and Key Distribution Centers support both, with TCP available for larger exchanges.
Kart 72
Soru
20/TCP — which FTP role?
Cevap
The server side of FTP's default active-mode data connection. Passive mode negotiates a different server port.
Kart 73
Soru
179/TCP — which routing protocol?
Cevap
BGP. Border Gateway Protocol peers use a TCP session to exchange routing information.
Kart 74
Soru
PostgreSQL — customary default port and transport?
Cevap
TCP 5432. PostgreSQL servers normally use it unless configured or compiled with another default.
Kart 75
Soru
500/UDP — which IPsec setup protocol?
Cevap
IKE, the Internet Key Exchange protocol. It negotiates IPsec security associations and commonly moves to UDP 4500 when NAT traversal is used.
Kart 76
Soru
137/UDP — which NetBIOS service?
Cevap
NetBIOS Name Service. It handles name registration and lookup in legacy NetBIOS over TCP/IP environments.
Kart 77
Soru
SMTP message submission — normal port and transport?
Cevap
TCP 587. It separates authenticated client submission from server-to-server SMTP relay on TCP 25; STARTTLS is commonly used.
Kart 78
Soru
LDAP — conventional connection-oriented port and transport?
Cevap
TCP 389. Connectionless LDAP can use UDP 389, and implicit-TLS LDAP commonly uses TCP 636.
Kart 79
Soru
1701/UDP — which tunneling protocol?
Cevap
L2TP. It tunnels Layer 2 traffic but needs a separate security layer such as IPsec when confidentiality is required.
Kart 80
Soru
NetBIOS Datagram Service — common port and transport?
Cevap
UDP 138. It provides connectionless NetBIOS datagram delivery.
Kart 81
Soru
993/TCP — which mail-access service?
Cevap
IMAPS. It begins IMAP with implicit TLS for encrypted access to mail stored on a server.
Kart 82
Soru
LDAPS — commonly used implicit-TLS port and transport?
Cevap
TCP 636. LDAP can instead use TCP 389 and negotiate TLS with StartTLS.
Kart 83
Soru
PPTP control — port and transport?
Cevap
TCP 1723. The control channel uses that port; PPP payloads travel through GRE, which is IP protocol 47 rather than port 47.
Kart 84
Soru
139/TCP — which NetBIOS service?
Cevap
NetBIOS Session Service. It historically carried SMB sessions; direct-hosted SMB commonly uses TCP 445 instead.
Kart 85
Soru
POP3S — default port and transport?
Cevap
TCP 995. It uses implicit TLS for encrypted POP3 mail retrieval.
Kart 86
Soru
1812/UDP — which AAA service?
Cevap
RADIUS authentication and authorization. RADIUS accounting normally uses UDP 1813.
Kart 87
Soru
4500/UDP — which IPsec function?
Cevap
IPsec NAT Traversal. It carries IKE and UDP-encapsulated ESP across network address translation.
Kart 88
Soru
SIP signaling without implicit TLS — common port and transports?
Cevap
UDP or TCP 5060. SIP over TLS conventionally uses TCP 5061, and media streams use separately negotiated ports.
88 kart
Common Network Port Numbers Flashcards: Protocols, TCP/UDP & Uses
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