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Port 5501Hotline File Transfer

Port 5501 is primarily used for Hotline, a classic client-server software popular in the late 1990s for file sharing, messaging, and community building. This port specifically handles file transfer connections within the Hotline ecosystem, enabling users to upload and download files on Hotline servers efficiently. Despite its decline in mainstream use, some legacy systems or enthusiasts may still utilize this port for archival purposes or nostalgia communities..

inFile TransferNetwork Services
transport
tcp

single transport

in transit
cleartext

payload readable on path

assignment
unofficial

used by convention

risk
4/10

caution

lookups
7,830

rank 651 of 993 · top 66%

Technical Details

what runs on :5501

Port 5501 is dedicated to managing file transfers within the Hotline communication suite. Hotline was designed as a proprietary software platform to facilitate multi-user discussions, chat, file sharing, and news distribution. It uses separate TCP ports to segment different functionalities, with port 5501 dedicated specifically to file data streams between clients and servers.

When a file transfer is initiated, the Hotline client opens a connection on port 5501 to communicate directly with the server, transferring data packets reliably over TCP. This provides a consistent and orderly file transfer experience, leveraging TCP's error-checking and retransmission mechanisms to ensure complete data delivery. Since it focuses on direct client-to-server transfers, latency typically depends on network conditions but remains robust without the need for complex protocols on top of TCP.

Given its design during an era preceding widespread encryption, Hotline file transfer over port 5501 transmits data in plaintext. This simplicity makes implementation straightforward but introduces potential security concerns in modern networks, especially over untrusted environments.

Security Information

exposure of :5501

risk score

4/ 10caution

worth attention. how exposed you are depends on configuration — don't leave it reachable from the internet without a reason.

file transfer averages 4.1 across 114 ports — this one sits 0.1 below.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

unofficial

used by convention, not registered — what answers here varies by deployment

reachable over

tcp

every listening transport is another surface to filter at the edge

security overview

Common Vulnerabilities:

  • Because Hotline was developed before secure protocols became standard, data including credentials and transferred files are typically transmitted unencrypted, making interception and man-in-the-middle (MitM) attacks feasible.
  • Outdated Hotline server software may contain unpatched vulnerabilities that could allow unauthorized access, remote code execution, or denial of service attacks.
  • Weak or default authentication mechanisms can be easily exploited by malicious actors attempting unauthorized access.

Common Mitigations:

  • Employ network-level encryption such as VPNs or secure tunneling protocols to encapsulate Hotline traffic, providing confidentiality.
  • Restrict port 5501 access using firewall rules or access control lists (ACL) to only trusted hosts.
  • Regularly update and patch server software to fix known vulnerabilities.
  • Enforce strong password policies to mitigate brute-force or credential stuffing attacks.
  • Monitor network traffic on port 5501 for unusual use patterns indicative of malicious activity.

Related Ports

all 114 in file transfer →

the 8 most looked-up other ports in file transfer — 114 ports carry that label.

portservicerisk
:9080Groove RPCcaution
:17500Dropbox LAN Synccaution
:548Apple Filing Protocolcaution
:7000Vuze HTTPS Trackercaution
:1337PowerFolder P2Pcaution
:9001SharePoint Authoringcaution
:8080FilePhile Relaycaution
:1337WASTE Encrypted Sharingcaution

risk mix of the 8 listed

  • caution100%

1 of 8 encrypted