Reasons:

There can be 3 potential causes of Socket Timeout. 

• First, the machine hosting the Web server maybe unreachable e.g. an intermediate router or firewall has failed
  
• Second, the Web server hosting the URL maybe unreachable e.g. the Web service is down
  
• Third, the Web server may be up, but not able to create a usable socket in time (within about 20 seconds) e.g. the server is busy

Solutions:

In the properties file -  agent_home/conf/application.properties add two parameters with values as below. These may also help with the agent not getting into the “Unknown” state.
 
ae.connect.timeout=60     #timeout for establishing connection
ae.socket.timeout=120    #socket timeout: timeout for which the packets can be stalled without breaking connection.
 
Both are in seconds. Start with these values and increase it if you still see timeout errors. Values can be up to a few minutes.