---
name: "modbus_connect"
section: "3"
platform: "linux"
package: "libmodbus-dev"
version: "3.1.6-2.1"
release: "Debian 12 (Bookworm)"
platforms: ["linux"]
url: "https://new.carta.tech/modbus_connect"
---

# modbus\_connect(3)

establish a Modbus connection

## NAME

modbus\_connect - establish a Modbus connection

## SYNOPSIS

**int modbus\_connect(modbus\_t \****ctx***);**

## DESCRIPTION

The **modbus\_connect()** function shall establish a connection to a Modbus server, a network or a bus using the context information of libmodbus context given in argument.

## RETURN VALUE

The function shall return 0 if successful. Otherwise it shall return -1 and set errno to one of the values defined by the system calls of the underlying platform.

## EXAMPLE

```
modbus_t *ctx;
ctx = modbus_new_tcp("127.0.0.1", 502);
if (modbus_connect(ctx) == -1) {
    fprintf(stderr, "Connection failed: %s\n", modbus_strerror(errno));
    modbus_free(ctx);
    return -1;
}
```

## SEE ALSO

[**modbus\_close**(3)](/modbus_close/3.md)

## AUTHORS

The libmodbus documentation was written by Stéphane Raimbault \<stephane.raimbault@gmail.com\>