A message sending method in a network structure comprising a Software Defined Network, SDN, including a plurality of terminal devices (6001, 6002, 6003; 7001, 7002, 7003) and a nested Virtual Private Network, VPN, including a plurality of provider edge, PE, devices (6010, 6020; 7010, 7020), the method comprising: a controller (600; 700) acquiring address information of each terminal device (6001, 6002, 6003; 7001, 7002, 7003) in the SDN and generating routing information according to the acquired address information, the controller (600; 700) establishing a neighbor relationship between a gateway device (6100; 7100) and the controller in the SDN, wherein the gateway device (6100; 7100) in the SDN is connected to the VPN and is configured with a border gateway protocol, BGP, routing protocol, wherein at least one PE device (6010; 7010) in the VPN is connected to the gateway device (6100; 7100), the gateway device (6100; 7100) transmitting the routing information of the terminal devices (6001, 6002, 6003; 7001, 7002, 7003) generated in SDN to the PE devices (6010; 7010) in the VPN using the BGP routing protocol, and the gateway device (6100; 7100) enabling the PE devices (6010, 6020; 7010, 7020) in the VPN to acquire the routing information of the terminal devices (6001, 6002, 6003; 7001, 7002, 7003) in the SDN such that each of the several PE devices (6010, 6020; 7010, 7020) in VPN is configured to send a message to respective terminal devices (6001, 6002, 6003; 7001, 7002, 7003) in the SDN according to acquired routing information, the method being characterized by further comprising the controller extracting information needed to be transferred from locally-stored port data in the several terminal devices (6001, 6002, 6003; 7001, 7002, 7003) in the SDN during generating routing information, the terminal device (6001, 6002, 6003; 7001, 7002, 7003) in the SDN being a virtual machine, the controller mapping the extracted information as VPN routing information according to a mapping table, and the controller sending the VPN routing information to the gateway device (6100; 7100). a controller (600; 700) acquiring address information of each terminal device (6001, 6002, 6003; 7001, 7002, 7003) in the SDN and generating routing information according to the acquired address information, the controller (600; 700) establishing a neighbor relationship between a gateway device (6100; 7100) and the controller in the SDN, wherein the gateway device (6100; 7100) in the SDN is connected to the VPN and is configured with a border gateway protocol, BGP, routing protocol, wherein at least one PE device (6010; 7010) in the VPN is connected to the gateway device (6100; 7100), the gateway device (6100; 7100) transmitting the routing information of the terminal devices (6001, 6002, 6003; 7001, 7002, 7003) generated in SDN to the PE devices (6010; 7010) in the VPN using the BGP routing protocol, and the gateway device (6100; 7100) enabling the PE devices (6010, 6020; 7010, 7020) in the VPN to acquire the routing information of the terminal devices (6001, 6002, 6003; 7001, 7002, 7003) in the SDN such that each of the several PE devices (6010, 6020; 7010, 7020) in VPN is configured to send a message to respective terminal devices (6001, 6002, 6003; 7001, 7002, 7003) in the SDN according to acquired routing information, the method being characterized by further comprising the controller extracting information needed to be transferred from locally-stored port data in the several terminal devices (6001, 6002, 6003; 7001, 7002, 7003) in the SDN during generating routing information, the terminal device (6001, 6002, 6003; 7001, 7002, 7003) in the SDN being a virtual machine, the controller mapping the extracted information as VPN routing information according to a mapping table, and the controller sending the VPN routing information to the gateway device (6100; 7100). <EOS>