libmodbus"ERROR communication time out -12)

Hi,

Im running a C program for capturing a modbus data from a charge controller. The program works when I connected it to a local network but when I connected it through Internet I got this error message "ERROR Communication time out (-12)" and the value of results is much more different from the result when it was connected to a local network. Im wondering if there's a way to change the communication time out from modbus.h that will solve this problem? Here's the part of the program:

#include <stdio.h>
#include <stdlib.h>
#include <modbus/modbus.h>

#define SUNSAVERMPPT 0x01 /* MODBUS Address of the SunSaver MPPT */

int main(void)
{
 modbus_param_t mb_param;
 int ret;
 float adc_vb_f,adc_va_f,adc_vl_f,adc_ic_f,adc_il_f, Vb_f, Vb_ref, Ahc_r, Ahc_t, kWhc;
 float V_lvd, Ahl_r, Ahl_t, Power_out, Sweep_Vmp, Sweep_Pmax, Sweep_Voc, Vb_min_daily;
 float Vb_max_daily, Ahc_daily, Ahl_daily, vb_min, vb_max;
 short T_hs, T_batt, T_amb, T_rts;
 unsigned short charge_state, load_state, led_state;
 unsigned int hourmeter;
 unsigned short array_fault, load_fault, dip_switch, array_fault_daily, load_fault_daily;
 unsigned int alarm, alarm_daily;
 uint16_t data[50];

 /* Setup the serial port parameters */
 modbus_init_tcp(&mb_param, "192.168.1.1", 502); /* Add the appropriate path to your serial port */

 /* Open the MODBUS connection */
 if (modbus_connect(&mb_param) == -1) {
  printf("ERROR Connection failed\n");
  exit(1);
 }

 /* Read the RAM Registers */
 ret = read_input_registers(&mb_param, SUNSAVERMPPT, 0x0008, 45, data);

 /* Close the MODBUS connection */
 modbus_close(&mb_param);

 /* Convert the results to their proper values and print them out */
 printf("RAM Registers\n\n");

 adc_vb_f=data[0]*100.0/32768.0;
 printf("adc_vb_f = %.2f V\n",adc_vb_f);

 adc_va_f=data[1]*100.0/32768.0;
 printf("adc_va_f = %.2f V\n",adc_va_f);

 adc_vl_f=data[2]*100.0/32768.0;
 printf("adc_vl_f = %.2f V\n",adc_vl_f);

 adc_ic_f=data[3]*79.16/32768.0;
 printf("adc_ic_f = %.2f A\n",adc_ic_f);

 adc_il_f=data[4]*79.16/32768.0;
 printf("adc_il_f = %.2f A\n",adc_il_f);

 T_hs=data[5];
 printf("T_hs = %d °C\n",T_hs);

 T_batt=data[6];
 printf("T_batt = %d °C\n",T_batt);

 T_amb=data[7];
 printf("T_amb = %d °C\n",T_amb);

 T_rts=data[8];
 printf("T_rts = %d °C\n",T_rts);