Ggtl certificate verification method, if the server provides a complete certificate chain, will be compared with the CA certificate built in the system layer by layer. The consistency of certificate and signature means that the server certificate is ok. If the server does not provide a certificate chain, but the issuing certificate generally provides a download address, then the client needs to download the certificate from bottom to top, and then find the built-in CA certificate in the system and check it from top to bottom. If the signature is normal, the server certificate is normal.