Data Application

Service and Support

Data Application
  • What's the maximum length of a domain name when establishing a TCP connection ?

    50 bytes.

  • What's the maximum length for APN, user name, and password accordingly when the embedded SIMCom TCPIP is adopted ?

    50 bytes.

  • Will the IP address be changed when the user set TCPIP at different time ?

    For a public network SIM card, the IP address will not be changed; if the SIM card is used only for internal network, the IP address may be changed. Users can obtain the IP address through AT + CIFSR / AT + SAPBR command based on the application.

  • How many ways are there to receive data in TCP/UDP connection ?

    1) There are two ways in opaque mode:

    a) Output the received data directly to UART.

    b) Read the received data manually through AT command.

    2) There is one way in transparent mode: Output the received data directly to UART.

  • In the TCP opaque mode, what's the maximum length of data sent by AT+CIPSEND ?

    The maximum length of data sent all at once depends on the actual network negotiation. Users can query this through AT+CIPSEND. The maximum value is 1460 bytes.

  • What's the difference between TCP and UDP ?

    TCP is a protocol based on connection; UE must connect to the far end before sending data. TCP provides reliable, sequential, and error-checking octet-streams among programs operating on devices connected to LAN, Intranet, and public Internet.

    UDP adopts simple connectionless transmission mode, with the minimum protocol mechanism. It has no handshake dialogue, which shows the unreliability of underlying network protocol to user programs. There's no guarantee of delivery, ordering, or duplicate protection.

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