1restmbmaster(8)             Rest API Modbus master             restmbmaster(8)
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4

NAME

6       restmbmaster — Rest API gateway to Modbus slaves
7

SYNOPSIS

9       restmbmaster -c CONNECT_URI -p PORT
10       restmbmaster -f FILE
11       restmbmaster -h|-v
12

DESCRIPTION

14       restmbmaster  is  a  simple  daemon  that  allows user to access Modbus
15       slaves over Rest API. The slaves could be either connected over  serial
16       line (Modbus RTU protocol), or over TCP (Modbus TCP protocol).
17

OPTIONS

19       -h, --help
20              Print help text to console and exit.
21
22       -v, --version
23              Print version information to console and exit.
24
25       -g, --debug
26              Turns on debugging messages. Repeating the option increases ver‐
27              bosity.
28
29       -c CONNECT_URI, --connect CONNECT_URI
30              Specifies the target Modbus bus to connect  to.  Supported  for‐
31              mats:
32
33              tcp://HOSTNAME[:PORT]
34
35                     Example: tcp://test.abc:1000
36
37                     Default PORT: 502
38
39              rtu:DEVICEPATH[?baud=BAUDRATE]
40
41                     Example: rtu:/dev/ttyS0?baud=9600
42
43                     Default BAUDRATE: 115200
44
45       -p PORT, --port PORT
46              Specifies TCP port on which the webserver is listening and where
47              the Rest API is exposed.
48
49       -f FILE, --config FILE
50              Load the specified configuration file.
51

REST API

53       The API is quite simple. Only "GET" (read) and  "PUT"  (write)  methods
54       are supported. The "Content-Type" is always "text/plain" for both "GET"
55       and "PUT". The path in the URL has following format:
56
57       http://HOSTNAME:PORT/slaves/SLAVE_ADDRESS/OBJECT_FAM‐
58       ILY/OBJECT_ADDRESS[?count=OBJECT_COUNT]
59
60              SLAVE_ADDRESS — Address of the slave to communitate with, number
61              in range from 0 to 255.
62
63              OBJECT_FAMILY — Is a  string  to  identify  the  family  of  the
64              objects. It is one of:
65
66                     coils — To access coils (RW).
67
68                     discrete-inputs — To access discrete inputs (RO).
69
70                     input-registers — To access input registers (RO).
71
72                     holding-registers — To access holding registers (RW).
73
74              OBJECT_ADDRESS  — Address of the object according to the family.
75              It is an integer number, starting from 0.
76
77              OBJECT_COUNT — Number of objects to read or write,  starting  at
78              OBJECT_ADDRESS. It is an integer number, starting from 0. If not
79              specified, defaults to 1.
80
81       The content being returned by "GET" method is a value of the object  as
82       a  plain  integer number in the text. If values of multiple objects are
83       requested, they are separated by a single space.  Same  format  applies
84       for the "PUT" method.
85

EXAMPLES

87       To run connecting to Modbus TCP:
88
89       $ restmbmaster -c tcp://test.abc:1000 -p 8080
90
91       To run connecting to Modbus RTU:
92
93       $ restmbmaster -c rtu:/dev/ttyS0?baud=9600 -p 8080
94
95       To run according to the configuration from file:
96
97       $ restmbmaster -f myconfig.conf
98
99       When restmbmaster is running, one can use for example curl to communicate with Modbus slaves.
100       In the following example, slave with address 55 is queried for the value of input register with address 10:
101
102       $ curl http://127.0.0.1:8080/slaves/55/input-registers/10
103       34
104
105       It is possible to query multiple registers (in sequence) at once:
106
107       $ curl http://127.0.0.1:8080/slaves/55/input-registers/10?count=4
108       34 78 234 2
109
110       To write new value (434) to holding register 20 the "PUT" method has to
111       be used:
112
113       $ curl http://127.0.0.1:8080/slaves/55/holding-registers/20 -d "434" -H "Content-Type: text/plain" -X PUT
114
115       It is also possible to write to a sequence of registers (20-26):
116
117       $ curl http://127.0.0.1:8080/slaves/55/holding-registers/20 -d "434 48 32 92 1 0 3" -H "Content-Type: text/plain" -X PUT
118

SEE ALSO

120       restmbmaster.conf(5),
121

AUTHOR

123       Jiri Pirko is the original author and current maintainer of  restmbmas‐
124       ter.
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128restmbmaster                   26 December 2019                restmbmaster(8)