How to Troubleshoot the \"CURL ERROR: Recv failure: Connection reset by peer\" Error in PHP?

CURL Error: Recv Failure: Connection Reset by Peer - PHP Curl

Introduction

When attempting to establish a connection to a remote server via PHP's CURL, developers may encounter the error message "CURL ERROR: Recv failure: Connection reset by peer." This frustrating issue can stem from various causes, typically related to TCP/IP issues, kernel bugs, or PHP/CURL bugs. This article explores the potential causes and offers possible solutions to resolve this pesky error.

Possible Causes and Solutions

TCP/IP Issues

• Upgrade your OS or consult your web hosting provider. Connection issues may arise due to outdated or buggy TCP/IP configurations. Consider updating your operating system or reaching out to your hosting provider for assistance.

Kernel Bug

• Refer to reported bug reports. In certain Linux kernel versions (e.g., post-v2.6.17), TCP window scaling issues have been documented. Investigate the following bug reports for more information:

  • https://bugs.launchpad.net/ubuntu/ source/linux-source-2.6.17/ bug/59331
  • https://bugs.launchpad.net/ubuntu/ source/linux-source-2.6.20/ bug/89160

PHP & CURL Bug

• Update your PHP and CURL versions. PHP/5.3.3 and earlier versions are known to have significant bugs related to this error. Consider upgrading to a more recent release of PHP and CURL. Refer to the following bug reports for further details:

  • https://bugs.php.net/bug.php?id=52828
  • https://bugs.php.net/bug.php?id=52827
  • https://bugs.php.net/bug.php?id=52202
  • https://bugs.php.net/bug.php?id=50410

Maximum Transmission Unit (MTU)

• Check your network connection's MTU size. A change from the default MTU size of 1500 bytes can lead to connection resets. If you have configured a VPN, verify that the MTU settings are correct.

Firewall: iptables

• Inspect your firewall rules. Ensure that port 80 is accessible on the remote server and that no iptables rules are blocking the connection. Review and adjust your iptables configuration accordingly.

Experimentation

• Try a different server. Connect to a different server and run your script to determine if the issue is server-specific or a broader network configuration problem.

Other Code-Related Issues

SSL

• Verify SSL settings. If the remote server URL uses HTTPS, improper SSL configurations can cause this error. Ensure that OpenSSL is installed and enabled. In your code, add the following lines:

  • curl_setopt($c, CURLOPT_SSL_VERIFYPEER, false);
  • curl_setopt($c, CURLOPT_SSL_VERIFYHOST, false);

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