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5. TCP/IP-Related AT Commands
Parameters
•
<link ID>
: ID of network connection (0~4), used for multiple connections.
•
<type>
: string parameter indicating the connection type:
"TCP"
,
"UDP"
or
"SSL"
.
•
<remote IP>
: string parameter indicating the remote IP address.
•
<remote port>
: remote port number.
•
[<UDP local port>]
: optional; UDP port of ESP8266.
•
[<UDP mode>]
: optional. In the UDP transparent transmission, the value of this parameter has to be 0.
‣
0
: the destination peer entity of UDP will not change; this is the default setting.
‣
1
: the destination peer entity of UDP can change once.
‣
2
: the destination peer entity of UDP is allowed to change.
⚠
Notice:
To use
<UDP mode>
,
<UDP local port>
must be set first.
Example
AT+CIPSTART="UDP","192.168.101.110",1000,1002,2
For more information please see:
ESP8266 AT Command Examples
.
Establish SSL Connection
Set
Command
AT+CIPSTART=[<link ID>,]<type>,<remote IP>,<remote port>[,<TCP keep alive>]
Response
OK
or
ERROR
If the TCP connection is already established, the response is:
ALREADY CONNECT
Parameters
•
<link ID>
: ID of network connection (0~4), used for multiple connections.
•
<type>
: string parameter indicating the connection type:
"TCP"
,
"UDP"
or
"SSL"
.
•
<remote IP>
: string parameter indicating the remote IP address.
•
<remote port>
: the remote port number.
•
[<TCP keep alive>]
: detection time interval when TCP is kept alive; this function is disabled by
default.
‣
0
: disable the TCP keep-alive function.
‣
1 ~ 7200
: detection time interval, unit: second (s).
Notes
•
ESP8266 can only set one SSL connection at most.
•
SSL connection does not support UART-Wi-Fi passthrough mode (transparent transmission).
•
SSL connection needs a large amount of memory; otherwise, it may cause system reboot. The
command
AT+CIPSSLSIZE=<size>
can be used to enlarge the SSL buffer size.
Example
AT+CIPSTART="SSL","iot.espressif.cn",8443
Espressif
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2017.05