Implement cometClient.connect() (Listing 13.56)
Ignore the duplicated connection (Listing 13.58)
Implement the validation of cometClient#url setting
Implement success callback for comet client (Listing 13.63)
Support X-Access-Token header (Listing 13.67)
Implement the request header which depends to the previous response token(Listing 13.69)
Implement the feature tests (Listing 13.70)
Implement basis of the function 'client.notify'
Implement client#notify (ch13.4.7)