What This Error Means
The “Pool Connection Error” — also displayed as “Stratum connection failed,” “Pool 1: not connected,” “Connection refused,” “DNS resolution failed,” or “Socket connect failed” — means your ASIC miner has network connectivity but cannot establish or maintain a connection to the configured mining pool. The Stratum protocol (stratum+tcp:// or stratum+ssl://) is the communication standard between miners and pools. When this connection fails, the miner has network access but cannot receive work or submit shares.
This error is distinct from a general network error. With a pool connection error, the miner typically has a valid IP address and you can access its web interface — it just cannot reach the mining pool server. This can be caused by configuration errors, pool-side issues, DNS problems, or network-level blocking.
Common Causes
- Incorrect pool URL or port — The pool address entered in the miner configuration is wrong, misspelled, or using an incorrect port number. This is the most common cause, especially after manual configuration or switching pools.
- Pool server is down — The mining pool itself is experiencing downtime, maintenance, or DDoS attacks. Even major pools have occasional outages.
- DNS resolution failure — The miner cannot resolve the pool hostname to an IP address. This happens when the DNS server configured on the miner (or the router’s DNS) is not responding.
- Firewall or ISP blocking — A local firewall, router configuration, or ISP-level blocking is preventing outbound connections on the mining port (commonly 3333, 25, or other ports used by pools).
- Incorrect worker name or password — Some pools reject connections with invalid authentication. While many pools accept any worker name, some require specific formatting.
- SSL/TLS mismatch — The miner is configured for stratum+ssl:// but the pool does not support encrypted connections on that port, or vice versa.
Step-by-Step Fix
Step 1: Verify Pool URL and Port
Log into the miner web interface and navigate to the pool configuration (Miner Configuration on Antminer, Settings on Whatsminer). Double-check the pool URL character by character against the pool’s official configuration page. Common mistakes include:
- Missing “stratum+tcp://” prefix (some miners require it, others do not)
- Wrong port number (the port determines the difficulty level — using the wrong port may not connect)
- Typos in the hostname (e.g., “stratun” instead of “stratum”)
- Using HTTP/HTTPS URLs instead of stratum protocol URLs
Step 2: Check Pool Status
Visit the mining pool’s website from your computer or phone. Most pools display their server status on the homepage or a dedicated status page. Check if the pool is experiencing downtime. Also check the pool’s social media (Twitter/X, Telegram, Discord) for outage announcements. If the pool is down, wait for it to recover or switch to your backup pool.
Step 3: Test DNS Resolution
From a computer on the same network as the miner, test if the pool hostname resolves:
# Windows
nslookup stratum.slushpool.com
ping stratum.slushpool.com
# Linux/Mac
dig stratum.slushpool.com
ping stratum.slushpool.comIf DNS resolution fails from your computer too, your DNS server is the problem. Try changing the DNS server on your router to a public DNS like Google (8.8.8.8), Cloudflare (1.1.1.1), or Quad9 (9.9.9.9). On some miners, you can set a custom DNS server directly in the network configuration.
Step 4: Configure Backup Pools
Most ASIC miners support 3 pool configurations (Pool 1, Pool 2, Pool 3). Always configure at least 2 pools so the miner can failover. Set your primary pool as Pool 1, a backup pool (different server or different pool entirely) as Pool 2, and optionally a third backup. This ensures mining continues even when one pool is unreachable.
Step 5: Test Network Connectivity to the Pool
From a computer on the same network, test connectivity to the pool’s specific port:
# Windows (PowerShell)
Test-NetConnection stratum.slushpool.com -Port 3333
# Linux/Mac
nc -zv stratum.slushpool.com 3333
# or
telnet stratum.slushpool.com 3333If the connection fails from your computer, a firewall or ISP is blocking the port. Check your router’s firewall settings and try a different port offered by the pool.
Step 6: Check Router and Firewall Settings
Log into your router and verify that outbound connections on the mining port are not being blocked. Some routers with built-in security features may flag mining traffic. Disable any “application control,” “traffic shaping,” or “gaming mode” features that might interfere. If you use a separate firewall or UTM appliance, ensure mining ports are whitelisted.
Step 7: Try a Different Pool Temporarily
To isolate whether the issue is pool-specific or network-wide, temporarily configure a different mining pool. If the miner connects to the second pool, the issue is with the original pool (either their servers or a connectivity path to them). If the miner cannot connect to any pool, the issue is on your network side.
Advanced Diagnosis
Via SSH on the miner for connection diagnostics:
ssh root@[miner-ip]
# Test DNS resolution from the miner
nslookup [pool-hostname]
# Test connectivity to pool port
nc -zv [pool-hostname] [port]
# Check current connection status
cat /var/log/messages | grep -i "pool"
cat /var/log/messages | grep -i "stratum"
# Check network configuration
cat /etc/resolv.conf # DNS server settingsPacket capture: For persistent issues, a packet capture on your router or a mirror port can reveal exactly what is happening at the network level — whether DNS queries are failing, TCP SYN packets are being dropped, or the Stratum handshake is failing at a specific stage.
ISP-level blocking: Some ISPs, particularly in certain countries, block mining traffic on common ports. If you suspect ISP blocking, try using an SSL-encrypted pool connection (stratum+ssl://) on port 443 — this looks like normal HTTPS traffic and is harder for ISPs to identify and block.
When to Get Professional Help
Pool connection issues are almost always configuration or network problems rather than hardware faults. Professional repair is rarely needed for this error. However, seek help if:
- The miner’s Ethernet controller is not functioning properly (can’t reach any network device)
- The control board’s network stack is corrupted — firmware reflash may resolve this
- You have verified all configuration and network settings and the miner still cannot connect to any pool
D-Central Technologies can diagnose network-related hardware issues and provide setup assistance for miners with persistent pool connectivity problems. Submit a repair request here
Affected Models
Pool connection errors can affect any ASIC miner regardless of manufacturer. All Antminer, Whatsminer, Avalon, and other ASIC models use Stratum protocol for pool communication. The troubleshooting steps are largely the same across all models, though the web interface and configuration pages differ.
Related Error Codes
- Network Error / Can’t Find Miner — If you cannot reach the miner web interface, the issue is network connectivity, not pool connection
- Low Hashrate — Intermittent pool connectivity causes hashrate drops as the miner loses work between disconnections
- Firmware Update Failed — Corrupted firmware can break the network stack
Frequently Asked Questions
Which mining pool should I use?
For decentralization and the health of the Bitcoin network, consider pools that do not already control a large percentage of hashrate. Popular options include Braiins Pool (formerly Slush Pool), Ocean, DEMAND, CKPool, and Solo CKPool for solo mining. Each pool has different fee structures, payout methods (PPS, FPPS, PPLNS), and minimum payout thresholds. Choose based on your priorities — maximum revenue, decentralization support, or solo mining attempts.
What is the difference between stratum+tcp and stratum+ssl?
stratum+tcp sends mining data unencrypted, while stratum+ssl encrypts the connection with TLS/SSL. For most home miners, either works fine. stratum+ssl provides protection against man-in-the-middle attacks that could redirect your hashrate to an attacker’s wallet. It also helps bypass ISP traffic shaping that targets unencrypted mining traffic. The performance overhead of encryption is negligible.
My miner keeps disconnecting from the pool every few hours — why?
Intermittent disconnections are commonly caused by: unstable internet connection (check your router logs for WAN disconnections), DNS server timeouts (switch to a more reliable DNS), router NAT table overflow (restart your router, or upgrade to one with a larger NAT table), or the pool itself having intermittent issues (check pool uptime statistics). Configure backup pools to maintain mining during brief disconnections.
Can I mine to multiple pools simultaneously?
Standard ASIC miners do not support simultaneous multi-pool mining out of the box. The Pool 1/2/3 configuration is for failover, not load balancing. However, some third-party firmware (like Braiins OS+) supports features like hash distribution across pools. For most home miners, a single primary pool with backup failover is the recommended configuration.