Connection Issue Analysis

When attempting to push code to GitHub on Windows systems, developers may encounter the error: Failed to connect to github.com port 443: Timed out. This prevents both Git operations and web access to GitHub services.

Troubleshooting Approach

The initial assumption might be proxy configuration issues. After disabling proxies, if the problem persists, the following steps can resolve timeout errors:

// Clear global proxy settings
git config --global --unset http.proxy

Next, visit a DNS lookup service to obtain current IP addresses for:

• github.com
• github.global.ssl.fastly.net

Add these mappings to the system hosts file located at C:\Windows\System32\drivers\etc\hosts:

140.82.114.4    github.com
199.232.69.194  github.global.ssl.fastly.net

Finally, flush the DNS cache and retry the operation:

ipconfig /flushdns

DNS Resolution Process

This solution works becuase it bypasses DNS lookup delays by creating direct IP mappings. Understanding why requires examining the complete URL resolution process:

1. Browser Cache Check: The browser first checks its internal DNS cache for recent lookups
2. System Cache Query: If not found locally, the system checks the hosts file for manual mappings
3. Local DNS Server Request: When no local maping exists, a query is sent to the ISP's DNS server
4. Recursive DNS Lookup: The local DNS server performs hierarchical queries:
   • Root name servers (.com, .org, etc.)
   • Top-level domain servers
   • Authoritative name servers for the specific domain
5. Response Caching: Results are cached at multiple levels for future requests

By manually configuring the hosts file, we eliminate several network hops in this process, directly mapping domain names to IP addresses without external DNS queries.

Network Communication Sequence

Once the IP address is resolved, the browser establishes communication through:

1. TCP Connection: Three-way handshake to establish reliable connection
2. HTTP Request: Browser sends request with method, headers, and body
3. Server Processing: Remote server processes and responds to the request
4. Connection Termination: Four-way handshake to gracefully close TCP connection
5. Content Rendering: Browser parses response data and renders content

The DNS cache refresh resolves GitHub connectivity issues because it clears stale entries and forces fresh lookups, ensuring accurate IP resolution for subsequent connections.