What is SYN_SENT socket status?

When dealing with Network issues one of the linux command that comes handy is 'netstat’

 netstat -an or netstat -an | grep “remote ip”

This command shows all the sockets in the system. Each socket has various status. For example, a socket can be in ‘ESTABLISHED’ status or in ‘LISTENING’ status.

One important status we may come across is ‘SYN_SENT’. When we see a socket in this status, it most probably indicates a Firewall issue, i.e the remote host you are trying to reach is NOT reachable due to a firewall block.

Note that the SYN_SENT status will not remain for long time. It only lasts for couple of seconds. So, you have to be quick in running the netstat command (perhaps in another terminal window)

When the client initiates a connection to Server, it first sends a SYN package. At this point the socket status changes to ‘SYN_SENT’. If the remote server is reachable and working, the client will receive a ‘SYN + ACK’, for which the client will send a ‘ACK’ and thus forms a TCP connection.

How to save cost in AWS? (WIP)

1. Stop all the instances that are not required.
2. Select appropriate EC2 instance
3. Reserve instance (May not be required for Non-production servers if they can be stopped when not required)
4. Select appropriate storage type to store different type of data
5. Use the  advisor available in the AWS portal
6. Business support can be taken only for production and non-production can be without any support.
 

Types of Monitoring

1. Domain monitoring (To keep an eye on the domain expiry for renewal)
2. Device Monitoring (IPS, Firewall, Switch, F5 Load Balancer, etc)
3. Operating System/ VM monitoring (CPU, Memory, I/O, Disk Utilization, etc)
4. Server monitoring (JVM, GC cycles, Mbeans, etc)
5. Architecture monitoring (Real time Deployment architecture monitoring)
6. Service monitoring (URL monitoring)
7. Application monitoring (Slow Transactions)
8. Log monitoring(End user activity)