生成证书
首先：需要安装 Openssl
以下是 openssl 命令
//生成 CA 证书
1.openssl genrsa -out rootCA.key 2048
2.openssl req -x509 -new -nodes -key rootCA.key -sha256 -days 3650 -subj
"/C=CN/ST=Shandong/L=jinan/O=yunding/OU=platform/CN=rootCA" -out rootCA.crt
//生成服务端证书
1.openssl genrsa -out outkey/IoTServerEmq.key 2048 （IoTServerEmq.key RSA 加密的）
2.openssl req -new -key outkey/IoTServerEmq.key -out outkey/IoTServerEmq.csr -subj
/C=CN/ST=Shandong/L=Jinan/O=yunding/OU=Iot/CN=IoTServerEmq
3.openssl pkcs8 -topk8 -in outkey/IoTServerEmq.key -out outkey/IoTServerEmq.pem -nocrypt
4.openssl x509 -req -in outkey/IoTServerEmq.csr -out outkey/IoTServerEmq.crt -CA
outkey/rootCA.crt -CAkey outkey/rootCA.key -CAcreateserial -days 10950 -passin pass:password
-extfile outkey/openssl3.cfg -extensions v3_req
//生成 client 证书
1.openssl genrsa -out outkey/IoTClientDm.key 2048
2.openssl req -new -key outkey/IoTClientDm.key -out outkey/IoTClientDm.csr -subj
/C=CN/ST=Shandong/L=Jinan/O=yunding/OU=Iot/CN=IoTClientDm
3.openssl pkcs8 -topk8 -in outkey/IoTClientDm.key -out outkey/IoTClientDm.pem -nocrypt
（IoTClientDm.pem 不加密的）
4.openssl x509 -req -in outkey/IoTClientDm.csr -out outkey/IoTClientDm.crt -CA
outkey/rootCA.crt -CAkey outkey/rootCA.key -CAcreateserial -days 36500 -passin pass:password
-extfile outkey/openssl3.cfg -extensions v3_req
生成如下文件：
