Socket limits in API mode

Note For NB-IoT, TCP support is dependent on the network. Contact your network provider for details.

In API mode there are a fixed number of sockets available; see Supported sockets. When a Transmit (TX) Request: IPv4 - 0x20 frame is sent to the XBee Smart Modem for a new destination, it creates a new socket. The exception to this is when using the UDP protocol with the C0 source port, which allows unlimited destinations on the socket created by C0 (Source Port). If no more sockets are available, the device sends back a Transmit (TX) Status - 0x89 frame with a Resource Error. The Resource Error resolves when an existing socket is closed. An existing socket may be closed when the socket times out (see TM (IP Client Connection Timeout) and TS (IP Server Connection Timeout)) or when the socket is closed via a TX request with the CLOSE flag set.

In API mode each socket has a maximum number of pending Transmit (TX) Requests allowed. When a Transmit (TX) Request: IPv4 - 0x20 frame is sent to the XBee Smart Modem for an existing destination, it sends that request using the socket for that destination. If the number of pending Transmit (TX) Requests would be exceeded for the socket, the device sends back a Transmit (TX) Status - 0x89 frame with a Resource Error indicating that the device is not able to send the request and should retry again later. The Resource Error resolves when a Transmit (TX) Request that is pending on the socket is transmitted; this is indicated by the Transmit (TX) Status frame for the request.