Ping fails. Is the service still reachable?
The target may restrict ICMP. Testing the actual service port checks whether a TCP connection can still be established.
TCP connectivity guide
Test server port connectivity from Vietnam
When a website will not open, check whether its target port accepts a TCP connection. Then use DNS, Ping and HTTP results to decide what to investigate next.
- Vietnam node perspectives
- Domain or IP and port
- Connection time comparison
When should you test TCP first?
Why does port 443 time out?
Check the port, service listener and firewall rules. Compare nodes in other regions to narrow down network or service issues.
Only some Vietnam paths have problems?
Compare the same target at the same time. Check resolved IPs and HTTP responses, then repeat the test before drawing conclusions.
Start in three steps
1
Select TCP
Open the homepage, switch to TCP and enter the domain or IP you want to test.
2
Enter the service port
HTTPS commonly uses 443 and HTTP commonly uses 80. Use the port configured for your service.
3
Compare connection results
Check which nodes connect, which time out and whether connection times differ by region.
Understand the results
| Observation | Next step |
|---|---|
| TCP connects, but the website does not open | Check TLS, HTTP status, authentication and application logs. A successful connection does not prove the application works. |
| The target port times out | Check the IP, port, listener, firewall and network path. A single timeout does not identify one definitive cause. |
| Some nodes take much longer | Check the resolved addresses and repeat at different times to investigate regional or ISP differences. |
Test direction and limitations
This test measures TCP connectivity and connection time from the probe network to the target. The target may be in Vietnam or elsewhere. It does not directly measure access from China to Vietnam, download bandwidth, file transfer speed or a complete network route.
After the port connects, check the real request
Use HTTP to check the website response, DNS to verify resolution and Ping to compare basic latency.