FiveM frequently communicates over HTTPS. Many antivirus suites (e.g., Norton, McAfee, Kaspersky) and firewalls (including Windows Defender Firewall with advanced rules) employ or "Secure Web Gateway" features. These tools intercept the encrypted stream, acting as a man-in-the-middle. If the inspection engine fails to reassemble the stream correctly, it will abruptly close the connection, generating cURL error 56 on the FiveM client.

The primary culprits fall into three categories: network instability (packet loss or MTU mismatches), aggressive security middleware (firewalls or SSL inspection), and server-side resource misconfiguration (improper HTTP timeouts or chunked encoding errors).

cURL error 56 differs fundamentally from a connection refusal (error 7) or timeout (error 28). It signifies a failed transaction within an otherwise open socket. In FiveM, this typically manifests during large file transfers (e.g., downloading a 500MB vehicle pack from a server), streaming audio from a radio resource, or when a proxy or CDN prematurely closes the connection. The error is rarely a problem with the cURL library itself; rather, it is a symptom of environmental interference.

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