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1Repair Windows errors before they cause bigger problems2Scan for outdated or missing drivers - takes under a minute3Clear out junk files and repair common Windows errors“Connection reset by peer” is a TCP symptom, not a single WordPress bug. The endpoint on the other side of a connection—or a proxy, firewall, or load balancer between them—closed the connection unexpectedly. Fix it by identifying which hop failed, matching the exact error to that layer, and then checking the relevant web server, PHP-FPM, TLS, proxy, firewall, plugin, or hosting settings.
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The same symptom can appear when a browser reaches your origin, when Nginx talks to PHP-FPM, or when WordPress uses PHP/cURL to call an external API. The error text and timestamp tell you which path to investigate.
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What “connection reset by peer” means in WordPress
TCP connections have two endpoints, but traffic often passes through several intermediaries. A reset means one endpoint sent a TCP reset instead of completing or cleanly closing the exchange. It does not, by itself, identify whether the cause was WordPress, PHP, Nginx, a reverse proxy, a firewall, or the remote service.
Start by drawing the path involved in the failing action:
- Inbound page request: browser → DNS/CDN or proxy → web server → PHP-FPM → WordPress.
- Outbound API request: WordPress/PHP/cURL → host firewall or proxy → internet → remote API.
- Internal upstream request: Nginx → FastCGI socket or PHP-FPM TCP address.
- Plugin integration: WordPress or a plugin → its external service, sometimes through a separate TLS or proxy path.
WordPress support describes cURL error 35 as usually server-related and recommends checking the hosting provider, Cloudflare, firewall rules, and caching. That guidance is useful, but “server-related” still covers several different layers, so test the path rather than replacing WordPress blindly.
Capture the failure before changing anything
Record one complete failure. Intermittent resets are much easier to diagnose when every log entry can be aligned to the same second.
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- Write down the UTC time, your client IP if known, the site hostname, request path, and whether the failure is repeatable.
- Copy the exact browser message or application error, including the HTTP status, cURL number, and any text following it.
- Note the scope: the whole site, only
/wp-admin/, media uploads, comments, cron, one plugin screen, or one remote integration. - Record what changed immediately beforehand: a WordPress or PHP update, plugin/theme update, certificate renewal, DNS change, firewall rule, proxy change, or deployment.
- At that timestamp, save relevant Nginx or Apache, PHP and PHP-FPM, WordPress debug, WAF/firewall, and remote-service logs.
Do not repeatedly retry a request that writes data until you know whether the first attempt reached the application. A reset can occur after a remote system accepted work but before your site received the response.
Use the error text to locate the failing hop
| Observed symptom | Most likely layer | First checks |
|---|---|---|
cURL error 35: OpenSSL SSL_connect: Connection reset by peer during an API call |
PHP/cURL/OpenSSL, an outbound proxy or firewall, or the remote API path | Run a verbose server-side cURL test; check PHP, cURL and OpenSSL versions, proxy variables, CA certificates, egress firewall rules, and the remote service. |
recv() failed (104: Connection reset by peer) while reading response header from upstream |
Nginx-to-PHP-FPM/FastCGI or another upstream | Check PHP-FPM health and fatal-error logs, socket or upstream address, worker limits, and timeout settings. |
| The error appears only in wp-admin, uploads, comments, or one integration | A plugin, theme, or that integration’s external service | Reproduce with the feature isolated; deactivate plugins one at a time and reinstall or remove the confirmed offender. |
| The same site works in development but resets in production | Environment-specific hosting, proxy, firewall, TLS, DNS, or resource conditions | Compare production and development web server, PHP, cURL, DNS, TLS, firewall, proxy, and process limits. |
The message is a location clue, not proof of a WordPress core defect. Test the underlying endpoint and TLS path before assigning blame to a plugin or theme.
Fix browser-to-origin resets
Confirm DNS and the endpoint being tested
Resolve the hostname from more than one network and compare the returned addresses with the server or proxy you intend to use. If some resolvers return an old address, clients can reach a retired host that closes connections. Test the origin directly only when your hosting setup permits it; bypassing a CDN or proxy can produce a different certificate or virtual host and is not a production fix by itself.
Check TLS termination and certificates
Use a verbose request from a machine outside the server:
curl -vI https://example.com/Look for the negotiated protocol, certificate name and validity, and the point at which the connection closes. A certificate mismatch, unsupported TLS version, or intermediary that terminates TLS incorrectly can reset the session before WordPress runs. Verify that the proxy’s certificate, origin certificate, SNI name, and encryption mode agree with the web server configuration.
Compare HTTP versions and intermediaries
Some failures are specific to a proxy’s HTTP/2 or HTTP/1.1 handling. Compare:
curl -v --http1.1 https://example.com/curl -v --http2 https://example.com/
If only one protocol fails, give the output and timestamp to the proxy or host administrator. Do not permanently disable a protocol solely because one test failed; identify the component that mishandles it.
Inspect firewall and WAF decisions
Review firewall, WAF, rate-limit, bot-control, and geo/IP rules for the client address and request path. A rule may reset a connection rather than return a friendly HTTP error. Temporarily narrowing a rule in a maintenance window can confirm the cause; restore protection immediately after the test.
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The Nginx message recv() failed (104: Connection reset by peer) while reading response header from upstream means Nginx connected to an upstream and lost it while waiting for response headers. In a typical WordPress stack, that upstream is PHP-FPM, although a reverse-proxied application can produce the same wording.
Check both logs at the same second
Read the Nginx error log and the PHP-FPM pool and service logs together. Search for worker exits, segmentation faults, out-of-memory kills, maximum-request warnings, startup failures, or PHP fatal errors. A reset with a simultaneous PHP-FPM crash points to the process or its resource limits; a reset with no PHP event warrants checking the socket, proxy, and host-level firewall.
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Verify the upstream endpoint
- Confirm that Nginx’s
fastcgi_passsocket or TCP address exists and belongs to the intended PHP version. - Check ownership and permissions on a Unix socket.
- Confirm PHP-FPM is running and has not been repeatedly restarting.
- Make sure a deployment did not leave Nginx pointing at an old socket.
After correcting configuration, validate it before reload:
nginx -tUse your operating system’s service manager to restart or reload the affected service only after the configuration test succeeds. If you do not administer the server, provide these checks to the host rather than editing production configuration blindly.
Review capacity and timeouts
Compare PHP-FPM pool settings such as pm.max_children, request termination limits, and listen backlog with the site’s traffic and memory. Also review Nginx FastCGI connect, send, and read timeouts. Raising a timeout can help a legitimately long request, but it cannot repair a PHP worker that is being killed for memory or a pool that is exhausted. Find the terminating event first.
A WordPress support case documents this exact Nginx reset while reading a PHP 8.2-FPM response header, illustrating why the PHP-FPM log and process health matter more than changing WordPress settings at random.
Resolve outbound cURL error 35
When a plugin, update check, license service, webhook, or WordPress HTTP API call reports cURL error 35: OpenSSL SSL_connect: Connection reset by peer, the failing direction is from your server to another service. The browser may still load the site normally.
Test from the server, not your laptop
Run a verbose request to the exact hostname and port from the production server:
curl -v https://api.example.net/Use the service’s documented endpoint and method when possible. Note DNS resolution, TCP connection, TLS handshake, certificate verification, negotiated protocol, and the point of failure. A successful browser test does not prove that the server’s network can reach the API.
Update the TLS client stack
Wordfence support notes that error 35 occurs when its service cannot be reached over SSL and identifies older cURL or proxying as possible causes. Update PHP, the cURL extension, and the system TLS libraries through your host’s supported package channel. Confirm the running PHP-FPM version, because command-line PHP and the PHP version used by the web server can differ.
Also verify that the system CA bundle is current and readable. Do not “fix” the error by disabling certificate verification; that removes protection against man-in-the-middle attacks.
Check proxies and egress controls
Inspect HTTPS_PROXY, HTTP_PROXY, and NO_PROXY environment variables, PHP proxy settings, container or hosting egress policies, and outbound firewall rules. A proxy that requires SNI, authentication, or a specific TLS mode can reset the handshake. Ask the host to trace outbound connections if you cannot inspect those controls.
Separate local and remote causes
If a direct cURL test fails for several unrelated endpoints, suspect the server’s TLS, proxy, or firewall path. If only one API fails, check that service’s status, allowlist requirements, rate limits, certificate chain, and request logs. If the remote service sees no request, the failure is before it reaches that service.
Correct reverse-proxy SSL forwarding
Plesk documents resets when Nginx is used as a reverse proxy without passing SSL information correctly. In configurations that proxy HTTPS upstreams, its stated remedy is enabling:
proxy_ssl_server_name on;Place the directive in the appropriate Additional nginx directives area for the affected virtual host, then test and reload Nginx according to your host’s procedure. The upstream hostname and SNI value must match the certificate and virtual host expected by the remote server. A directive copied into the wrong server block, or enabled without a correct upstream name, will not solve the problem.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Isolate a plugin or theme safely
When isolation is justified
Limit this branch to failures confined to one feature, such as an admin screen, media upload, comment submission, scheduled task, or third-party integration. If the entire site resets at the TCP layer, disabling random plugins is unlikely to address the real cause.
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Using the dashboard
- Take a backup and choose a maintenance window.
- Open Plugins → Installed Plugins.
- Deactivate one plugin, reproduce the exact request, and record the result.
- Continue one at a time until the failure disappears, then reactivate unaffected plugins.
- For the identified plugin, install a clean current release or remove it if the vendor cannot provide a compatible version. Check its PHP and WordPress requirements before reactivation.
Plesk lists corrupted WordPress plugins as a cause and recommends deactivating plugins individually, then reinstalling or deleting the one that triggers the error.
When wp-admin is inaccessible
Use the hosting control panel’s WordPress toolkit, a file manager to rename the plugin directory temporarily, or a controlled WP-CLI procedure if your host supports it. Rename only the suspected plugin directory, test, and restore the name after the test. Do not delete files before preserving a backup and the plugin version information.
Check themes and recovery mode
If disabling all plugins changes nothing, switch temporarily to a bundled default theme using the dashboard or your host’s recovery tools. WordPress Recovery Mode can identify a PHP fatal error, but it will not repair a network or TLS reset. Treat a recovery email or fatal stack trace as evidence about the failing code, not as proof that every connection-reset symptom has the same cause.
Compare development and production methodically
“It works locally” narrows the issue to an environmental difference. Compare the following rather than copying application files repeatedly:
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|---|---|
| Runtime | Are PHP, cURL, OpenSSL, WordPress, plugin, and theme versions identical? |
| Web stack | Is production using Nginx, Apache, PHP-FPM, a different socket, or different worker and timeout limits? |
| Network | Do DNS answers, IPv4/IPv6 routes, outbound ports, proxy variables, and firewall policies differ? |
| TLS | Does production terminate TLS at a CDN, load balancer, or reverse proxy, and does it pass the correct SNI and headers? |
| Resources | Are production memory, CPU, process, file-descriptor, or request quotas causing workers to be killed? |
| Scope | Does the failure affect the same URL, payload size, authentication state, and integration? |
Reproduce with the smallest request that fails, then add payload size, authentication, and plugin functionality back one variable at a time.
What to send your host or server administrator
Escalation is faster when the recipient can correlate the event without asking for another round of screenshots. Send:
- UTC timestamp and timezone, hostname, request path, HTTP method, and client/server IPs where available;
- the complete browser, cURL, Nginx, or Apache error line;
- matching Nginx/Apache, PHP-FPM, PHP, WordPress, WAF, and firewall log excerpts;
- verbose cURL output with secrets, cookies, authorization headers, and tokens removed;
- the PHP, cURL, OpenSSL, web-server, and WordPress versions;
- proxy, CDN, DNS, certificate, and firewall changes made before the incident;
- the exact plugin, theme, integration, or route that reproduces the reset; and
- whether the issue is constant, intermittent, protocol-specific, or limited to production.
If you cannot inspect Nginx, PHP-FPM, TLS, firewall, or proxy layers, managed WordPress hosting or server-support assistance is the appropriate escalation path. A generic router replacement or desktop utility cannot correct a reset generated inside the hosting stack.
Quick Recap
Prevent the next reset
- Keep PHP, cURL, OpenSSL, WordPress, plugins, and themes within supported versions, testing updates in staging first.
- Retain synchronized web-server, PHP-FPM, WordPress, and firewall logs with timestamps long enough to investigate intermittent failures.
- Monitor PHP-FPM restarts, memory exhaustion, worker saturation, upstream latency, TLS expiry, and failed outbound requests.
- Document every proxy, DNS, certificate, and firewall change and record which layer terminates TLS.
- Use least-privilege firewall rules and explicit allowlists for required integrations instead of broad, temporary exceptions.
- Keep a tested backup and a rollback plan for plugin, theme, PHP, and server configuration changes.
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