SimCom SIM7500 Series At Command Manual page 302

<link_num>
a numeric parameter that identifies a connection. The range of permitted values is 0 to 9.
<length>
a numeric parameter which indicates the length of sending data, it must be between1 and 1500.
<serverIP>
A string parameter that identifies the IP address of server.The IP address format consists of 4
octets,separated by decimal point:"AAA.BBB.CCC.DDD".
<serverPort>
a numeric parameter that identifies the port of TCP server, the range of permitted values is 0 to
65535.
NOTE: When open port as TCP, the port must be the opened TCP port;
When open port as UDP, the port may be any port.
But, for Qualcomm, connecting the port 0 is as an invalid operation.
<reqSendLength>
a numeric parameter that requested number of data bytes to be transmitted.
<cnfSendLength>
a numeric parameter that confirmed number of data bytes to be transmitted.
-1 the connection is disconnected.
0 own send buffer or other side's congestion window are full.
Note: If the <cnfSendLength> is not equal to the <reqSendLength>, the socket then cannot be used
further.
<err_info>
A string parameter that displays the cause of occurring error.
Examples
AT+CIPSEND=0,1
> S
OK
+CIPSEND: 0, 1, 1
AT+CIPSEND=1,1,"116.236.221.75",6775
> S
OK
+CIPSEND: 1, 1, 1
AT+CIPSEND=2,
>Hello<Ctrl+Z>
OK
+CIPSEND: 2,5,5
AT+CIPSEND=3,,"116.236.221.75",6775
SIM7500_SIM7600 Series_AT Command Manual_V1.07
Smart Machine Smart Decision
301 2017-12-25