modbus_new_tcp(3)

1MODBUS_NEW_TCP(3)              Libmodbus Manual              MODBUS_NEW_TCP(3)
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NAME

6       modbus_new_tcp - create a libmodbus context for TCP/IPv4
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SYNOPSIS

9       modbus_t *modbus_new_tcp(const char *ip, int port);
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DESCRIPTION

12       The modbus_new_tcp() function shall allocate and initialize a modbus_t
13       structure to communicate with a Modbus TCP/IPv4 server.
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15       The ip argument specifies the IP address of the server to which the
16       client wants etablish a connection.
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18       The port argument is the TCP port to use. Set the port to
19       MODBUS_TCP_DEFAULT_PORT to use the default one (502). It’s convenient
20       to use a port number greater than or equal to 1024 because it’s not
21       necessary to have administrator privileges.
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RETURN VALUE

24       The modbus_new_tcp() function shall return a pointer to a modbus_t
25       structure if successful. Otherwise it shall return NULL and set errno
26       to one of the values defined below.
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ERRORS

29       EINVAL
30           An invalid IP address was given.
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EXAMPLE

33           modbus_t *ctx;
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35           ctx = modbus_new_tcp("127.0.0.1", 1502);
36           if (ctx == NULL) {
37               fprintf(stderr, "Unable to allocate libmodbus context\n");
38               return -1;
39           }
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41           if (modbus_connect(ctx) == -1) {
42               fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
43               modbus_free(ctx);
44               return -1;
45           }
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AUTHORS

51       The libmodbus documentation was written by Stéphane Raimbault
52       <stephane.raimbault@gmail.com[1]>
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NOTES

55        1. stephane.raimbault@gmail.com
56           mailto:stephane.raimbault@gmail.com
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60libmodbus 3.0.6                   04/02/2014                 MODBUS_NEW_TCP(3)