SESKStuff Everyone Should Know
SESK: Stuff Everyone Should Know · sesk.info/aplus-smb-port

File sharing between Windows computers uses SMB. Which port does SMB use?

Port 445 is used for SMB.

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  1. 445 ✔
  2. 389
  3. 3389

Why: SMB (Server Message Block) uses port 445. Port 389 is LDAP directory lookups and 3389 is Remote Desktop. Port 445 is registered as 'Microsoft-DS'.

Huh, didn't know that: The same exam list also names the older NetBIOS ports, 137 to 139.

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References

Answer: 445. SMB (Server Message Block) uses port 445. Port 389 is LDAP directory lookups and 3389 is Remote Desktop. Port 445 is registered as 'Microsoft-DS'.

  1. IANA Service Name and Transport Protocol Port Number Registry CSV www.iana.org/assignments/service-names-port-numbers/service-names-port-numbers.csv
    microsoft-ds,445,tcp,Microsoft-DS
    Checked 2026-10-11.
  2. CompTIA A+ Core 1 (220-1201) V15 Exam Objectives lecbyo.files.cmp.optimizely.com/download/34be017cb73211ef8985a6f347fbf652
    Server Message Block (SMB)/Common Internet File System (CIFS)
    Checked 2026-10-11.

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