Overview
During FTP sessions, CuteFTP may display socket‑related errors indicating issues with connectivity, resource availability, or misconfigured settings. This article consolidates guidance for resolving three common socket errors:
- Socket Error 10055 – Insufficient Buffer Space
- Socket Error 10054 – Connection Reset by Peer
- Socket Error 2000 – Cannot Connect to Remote Server
Socket Error 10055
ERROR:
Can't read from data socket. Socket error = #10055
Cause
Error 10055 indicates the system lacks sufficient buffer space or has a full queue. This generally results from:
- Low system resources
- Too many applications running
- Insufficient physical memory
- A paging file (virtual memory) that is too small
- Low available disk space
- Excessive items in the CuteFTP transfer queue
Resolution
Try one or more of the following steps:
- Close unnecessary applications to free memory.
- Restart the computer to reset available resources.
- Clear completed transfers in CuteFTP’s Queue window:
- Right‑click the Queue window → Remove All
- Limit CuteFTP bandwidth usage:
- Go to Tools > Global Options > Transfer > General
- Set Global Bandwidth Limit to 500 KB/s or lower
- Increase virtual memory by enlarging the Windows paging file.
- Windows Vista users:
- Open Performance Information and Tools from Control Panel to adjust performance settings.
Socket Error 10054
ERROR:
Can't read from control socket. Socket error = #10054
Cause
Socket error 10054 means the connection was forcibly closed by the remote server or by network equipment. Common reasons include:
- Invalid FTP host address
- The remote server was restarted or stopped
- The server’s network interface is down
- Too many users logged in to the server
- Restrictions on your server account
- Recent browser upgrades affecting networking behavior
- Data connection settings incompatible with the server (PASV vs. PORT mode)
Resolution
Try the following:
- Verify the FTP host address is correct.
- Retry the connection later—the issue may be temporary.
- Confirm that the remote server is online and not overloaded.
- Ensure your server account has permission to connect.
- If the issue began after a browser upgrade, refer to KB 10294.
- Change the data connection type (PASV ↔ PORT):
- CuteFTP Home:
- Site Manager → Select site → Type tab → Set Data Connection Type to Use Port
- CuteFTP Professional:
- Site Manager → Right‑click site → Site Properties → Type tab → Set Data Connection Type to Use Port
- If this does not fix the issue, revert to Use global settings.
- In CuteFTP Professional, if the server cannot handle advanced features, limit transfers to one file at a time.
- If problems persist, the send/receive buffer size may be too high. See KB 10293 for instructions.
Socket Error 2000
ERROR:
Can't connect to remote server. Socket error = #2000
Possible accompanying message:
STATUS: Time zone synchronization failed.
Cause
The most common cause is port 21 being blocked by:
- Firewall software
- Hardware firewalls
- Proxy servers
- Misconfigured network security rules
Resolution
Ensure that port 21 is open for both inbound and outbound traffic.
Check and update:
- Local firewall software
- Router/firewall hardware
- Proxy server configuration
Consult your firewall or network device documentation for exact steps.