In one illustrative example, a radio modem device includes a serial interface adapted for connection to a host device via a wired serial link with use of a Point-to-Point Protocol (PPP) connection; a radio modem router coupled to the serial interface; a radio modem server coupled to the radio modem router; and radio frequency (RF) transceiver processing circuitry coupled to the radio modem router. The RF transceiver processing circuitry is configured to provide communications over a wireless link with a cellular network, establish a packet data service attachment with the cellular network, and maintain an attachment state of the attachment during operation of the radio modem device. The radio modem router is configured to receive data packets from the host device; remove a PPP wrapper of the data packets to reveal a destination IP address and a destination UDP or TCP port number; identify whether the destination IP address and the UDP or TCP port number match an IP address and UDP or TCP port number of the radio modem server; in response to identifying a mismatch between the IP addresses or the UDP or TCP port numbers: cause the data packets to be routed to a server, over the wireless link, using the attachment with the cellular network; and in response to identifying a match between the IP addresses and the UDP or TCP port numbers, cause the data packets to be routed to the radio modem server. The radio modem server is configured to receive the data packets from the radio modem router when the IP addresses and the UDP or TCP port numbers match; receive a command code in the data packets; and if the command code is for obtaining the attachment state of the attachment with the cellular network, then cause a response having the attachment state to be sent to the host device.