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/*
* Copyright © 2001-2013 Stéphane Raimbault <stephane.raimbault@gmail.com>
*
* SPDX-License-Identifier: LGPL-2.1+
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#ifndef _MSC_VER
#include <unistd.h>
#endif
#include <signal.h>
#include <sys/types.h>
#if defined(_WIN32)
# define OS_WIN32
/* ws2_32.dll has getaddrinfo and freeaddrinfo on Windows XP and later.
* minwg32 headers check WINVER before allowing the use of these */
# ifndef WINVER
# define WINVER 0x0501
# endif
/* Already set in modbus-tcp.h but it seems order matters in VS2005 */
# include <winsock2.h>
# include <ws2tcpip.h>
# define SHUT_RDWR 2
# define close closesocket
#else
# include <sys/socket.h>
# include <sys/ioctl.h>
#if defined(__OpenBSD__) || (defined(__FreeBSD__) && __FreeBSD__ < 5)
# define OS_BSD
# include <netinet/in_systm.h>
#endif
# include <netinet/in.h>
# include <netinet/ip.h>
# include <netinet/tcp.h>
# include <arpa/inet.h>
# include <netdb.h>
#endif
#if !defined(MSG_NOSIGNAL)
#define MSG_NOSIGNAL 0
#endif
#include "modbus-private.h"
#include "modbus-tcp.h"
#include "modbus-tcp-private.h"
#ifdef OS_WIN32
static int _modbus_tcp_init_win32(void)
{
/* Initialise Windows Socket API */
WSADATA wsaData;
if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0) {
fprintf(stderr, "WSAStartup() returned error code %d\n",
(unsigned int)GetLastError());
errno = EIO;
return -1;
}
return 0;
}
#endif
static int _modbus_set_slave(modbus_t *ctx, int slave)
{
/* Broadcast address is 0 (MODBUS_BROADCAST_ADDRESS) */
if (slave >= 0 && slave <= 247) {
ctx->slave = slave;
} else if (slave == MODBUS_TCP_SLAVE) {
/* The special value MODBUS_TCP_SLAVE (0xFF) can be used in TCP mode to
* restore the default value. */
ctx->slave = slave;
} else {
errno = EINVAL;
return -1;
}
return 0;
}
/* Builds a TCP request header */
static int _modbus_tcp_build_request_basis(modbus_t *ctx, int function,
int addr, int nb,
uint8_t *req)
{
modbus_tcp_t *ctx_tcp = ctx->backend_data;
/* Increase transaction ID */
if (ctx_tcp->t_id < UINT16_MAX)
ctx_tcp->t_id++;
else
ctx_tcp->t_id = 0;
req[0] = ctx_tcp->t_id >> 8;
req[1] = ctx_tcp->t_id & 0x00ff;
/* Protocol Modbus */
req[2] = 0;
req[3] = 0;
/* Length will be defined later by set_req_length_tcp at offsets 4
and 5 */
req[6] = ctx->slave;
req[7] = function;
req[8] = addr >> 8;
req[9] = addr & 0x00ff;
req[10] = nb >> 8;
req[11] = nb & 0x00ff;
return _MODBUS_TCP_PRESET_REQ_LENGTH;
}
/* Builds a TCP response header */
static int _modbus_tcp_build_response_basis(sft_t *sft, uint8_t *rsp)
{
/* Extract from MODBUS Messaging on TCP/IP Implementation
Guide V1.0b (page 23/46):
The transaction identifier is used to associate the future
response with the request. */
rsp[0] = sft->t_id >> 8;
rsp[1] = sft->t_id & 0x00ff;
/* Protocol Modbus */
rsp[2] = 0;
rsp[3] = 0;
/* Length will be set later by send_msg (4 and 5) */
/* The slave ID is copied from the indication */
rsp[6] = sft->slave;
rsp[7] = sft->function;
return _MODBUS_TCP_PRESET_RSP_LENGTH;
}
static int _modbus_tcp_prepare_response_tid(const uint8_t *req, int *req_length)
{
return (req[0] << 8) + req[1];
}
static int _modbus_tcp_send_msg_pre(uint8_t *req, int req_length)
{
/* Substract the header length to the message length */
int mbap_length = req_length - 6;
req[4] = mbap_length >> 8;
req[5] = mbap_length & 0x00FF;
return req_length;
}
static ssize_t _modbus_tcp_send(modbus_t *ctx, const uint8_t *req, int req_length)
{
/* MSG_NOSIGNAL
Requests not to send SIGPIPE on errors on stream oriented
sockets when the other end breaks the connection. The EPIPE
error is still returned. */
return send(ctx->s, (const char *)req, req_length, MSG_NOSIGNAL);
}
static int _modbus_tcp_receive(modbus_t *ctx, uint8_t *req) {
return _modbus_receive_msg(ctx, req, MSG_INDICATION);
}
static ssize_t _modbus_tcp_recv(modbus_t *ctx, uint8_t *rsp, int rsp_length) {
return recv(ctx->s, (char *)rsp, rsp_length, 0);
}
static int _modbus_tcp_check_integrity(modbus_t *ctx, uint8_t *msg, const int msg_length)
{
return msg_length;
}
static int _modbus_tcp_pre_check_confirmation(modbus_t *ctx, const uint8_t *req,
const uint8_t *rsp, int rsp_length)
{
/* Check transaction ID */
if (req[0] != rsp[0] || req[1] != rsp[1]) {
if (ctx->debug) {
fprintf(stderr, "Invalid transaction ID received 0x%X (not 0x%X)\n",
(rsp[0] << 8) + rsp[1], (req[0] << 8) + req[1]);
}
errno = EMBBADDATA;
return -1;
}
/* Check protocol ID */
if (rsp[2] != 0x0 && rsp[3] != 0x0) {
if (ctx->debug) {
fprintf(stderr, "Invalid protocol ID received 0x%X (not 0x0)\n",
(rsp[2] << 8) + rsp[3]);
}
errno = EMBBADDATA;
return -1;
}
return 0;
}
static int _modbus_tcp_set_ipv4_options(int s)
{
int rc;
int option;
/* Set the TCP no delay flag */
/* SOL_TCP = IPPROTO_TCP */
option = 1;
rc = setsockopt(s, IPPROTO_TCP, TCP_NODELAY,
(const void *)&option, sizeof(int));
if (rc == -1) {
return -1;
}
/* If the OS does not offer SOCK_NONBLOCK, fall back to setting FIONBIO to
* make sockets non-blocking */
/* Do not care about the return value, this is optional */
option = 1;
#if !defined(SOCK_NONBLOCK) && defined(FIONBIO)
#ifdef OS_WIN32
{
/* Setting FIONBIO expects an unsigned long according to MSDN */
u_long loption = 1;
ioctlsocket(s, FIONBIO, &loption);
}
#else
ioctl(s, FIONBIO, &option);
#endif
#endif
#ifndef OS_WIN32
/**
* Cygwin defines IPTOS_LOWDELAY but can't handle that flag so it's
* necessary to workaround that problem.
**/
/* Set the IP low delay option */
option = IPTOS_LOWDELAY;
rc = setsockopt(s, IPPROTO_IP, IP_TOS,
(const void *)&option, sizeof(int));
if (rc == -1) {
return -1;
}
#endif
return 0;
}
static int _connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen,
const struct timeval *ro_tv)
{
int rc = connect(sockfd, addr, addrlen);
#ifdef OS_WIN32
int wsaError = 0;
if (rc == -1) {
wsaError = WSAGetLastError();
}
if (wsaError == WSAEWOULDBLOCK || wsaError == WSAEINPROGRESS) {
#else
if (rc == -1 && errno == EINPROGRESS) {
#endif
fd_set wset;
int optval;
socklen_t optlen = sizeof(optval);
struct timeval tv = *ro_tv;
/* Wait to be available in writing */
FD_ZERO(&wset);
FD_SET(sockfd, &wset);
rc = select(sockfd + 1, NULL, &wset, NULL, &tv);
if (rc <= 0) {
/* Timeout or fail */
return -1;
}
/* The connection is established if SO_ERROR and optval are set to 0 */
rc = getsockopt(sockfd, SOL_SOCKET, SO_ERROR, (void *)&optval, &optlen);
if (rc == 0 && optval == 0) {
return 0;
} else {
errno = ECONNREFUSED;
return -1;
}
}
return rc;
}
/* Establishes a modbus TCP connection with a Modbus server. */
static int _modbus_tcp_connect(modbus_t *ctx)
{
int rc;
/* Specialized version of sockaddr for Internet socket address (same size) */
struct sockaddr_in addr;
modbus_tcp_t *ctx_tcp = ctx->backend_data;
int flags = SOCK_STREAM;
#ifdef OS_WIN32
if (_modbus_tcp_init_win32() == -1) {
return -1;
}
#endif
#ifdef SOCK_CLOEXEC
flags |= SOCK_CLOEXEC;
#endif
#ifdef SOCK_NONBLOCK
flags |= SOCK_NONBLOCK;
#endif
ctx->s = socket(PF_INET, flags, 0);
if (ctx->s == -1) {
return -1;
}
rc = _modbus_tcp_set_ipv4_options(ctx->s);
if (rc == -1) {
close(ctx->s);
ctx->s = -1;
return -1;
}
if (ctx->debug) {
printf("Connecting to %s:%d\n", ctx_tcp->ip, ctx_tcp->port);
}
addr.sin_family = AF_INET;
addr.sin_port = htons(ctx_tcp->port);
addr.sin_addr.s_addr = inet_addr(ctx_tcp->ip);
rc = _connect(ctx->s, (struct sockaddr *)&addr, sizeof(addr), &ctx->response_timeout);
if (rc == -1) {
close(ctx->s);
ctx->s = -1;
return -1;
}
return 0;
}
/* Establishes a modbus TCP PI connection with a Modbus server. */
static int _modbus_tcp_pi_connect(modbus_t *ctx)
{
int rc;
struct addrinfo *ai_list;
struct addrinfo *ai_ptr;
struct addrinfo ai_hints;
modbus_tcp_pi_t *ctx_tcp_pi = ctx->backend_data;
#ifdef OS_WIN32
if (_modbus_tcp_init_win32() == -1) {
return -1;
}
#endif
memset(&ai_hints, 0, sizeof(ai_hints));
#ifdef AI_ADDRCONFIG
ai_hints.ai_flags |= AI_ADDRCONFIG;
#endif
ai_hints.ai_family = AF_UNSPEC;
ai_hints.ai_socktype = SOCK_STREAM;
ai_hints.ai_addr = NULL;
ai_hints.ai_canonname = NULL;
ai_hints.ai_next = NULL;
ai_list = NULL;
rc = getaddrinfo(ctx_tcp_pi->node, ctx_tcp_pi->service,
&ai_hints, &ai_list);
if (rc != 0) {
if (ctx->debug) {
fprintf(stderr, "Error returned by getaddrinfo: %s\n", gai_strerror(rc));
}
errno = ECONNREFUSED;
return -1;
}
for (ai_ptr = ai_list; ai_ptr != NULL; ai_ptr = ai_ptr->ai_next) {
int flags = ai_ptr->ai_socktype;
int s;
#ifdef SOCK_CLOEXEC
flags |= SOCK_CLOEXEC;
#endif
#ifdef SOCK_NONBLOCK
flags |= SOCK_NONBLOCK;
#endif
s = socket(ai_ptr->ai_family, flags, ai_ptr->ai_protocol);
if (s < 0)
continue;
if (ai_ptr->ai_family == AF_INET)
_modbus_tcp_set_ipv4_options(s);
if (ctx->debug) {
printf("Connecting to [%s]:%s\n", ctx_tcp_pi->node, ctx_tcp_pi->service);
}
rc = _connect(s, ai_ptr->ai_addr, ai_ptr->ai_addrlen, &ctx->response_timeout);
if (rc == -1) {
close(s);
continue;
}
ctx->s = s;
break;
}
freeaddrinfo(ai_list);
if (ctx->s < 0) {
return -1;
}
return 0;
}
/* Closes the network connection and socket in TCP mode */
static void _modbus_tcp_close(modbus_t *ctx)
{
if (ctx->s != -1) {
shutdown(ctx->s, SHUT_RDWR);
close(ctx->s);
ctx->s = -1;
}
}
static int _modbus_tcp_flush(modbus_t *ctx)
{
int rc;
int rc_sum = 0;
do {
/* Extract the garbage from the socket */
char devnull[MODBUS_TCP_MAX_ADU_LENGTH];
#ifndef OS_WIN32
rc = recv(ctx->s, devnull, MODBUS_TCP_MAX_ADU_LENGTH, MSG_DONTWAIT);
#else
/* On Win32, it's a bit more complicated to not wait */
fd_set rset;
struct timeval tv;
tv.tv_sec = 0;
tv.tv_usec = 0;
FD_ZERO(&rset);
FD_SET(ctx->s, &rset);
rc = select(ctx->s+1, &rset, NULL, NULL, &tv);
if (rc == -1) {
return -1;
}
if (rc == 1) {
/* There is data to flush */
rc = recv(ctx->s, devnull, MODBUS_TCP_MAX_ADU_LENGTH, 0);
}
#endif
if (rc > 0) {
rc_sum += rc;
}
} while (rc == MODBUS_TCP_MAX_ADU_LENGTH);
return rc_sum;
}
/* Listens for any request from one or many modbus masters in TCP */
int modbus_tcp_listen(modbus_t *ctx, int nb_connection)
{
int new_s;
int yes;
struct sockaddr_in addr;
modbus_tcp_t *ctx_tcp;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
ctx_tcp = ctx->backend_data;
#ifdef OS_WIN32
if (_modbus_tcp_init_win32() == -1) {
return -1;
}
#endif
new_s = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
if (new_s == -1) {
return -1;
}
yes = 1;
if (setsockopt(new_s, SOL_SOCKET, SO_REUSEADDR,
(char *)&yes, sizeof(yes)) == -1) {
close(new_s);
return -1;
}
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
/* If the modbus port is < to 1024, we need the setuid root. */
addr.sin_port = htons(ctx_tcp->port);
if (ctx_tcp->ip[0] == '0') {
/* Listen any addresses */
addr.sin_addr.s_addr = htonl(INADDR_ANY);
} else {
/* Listen only specified IP address */
addr.sin_addr.s_addr = inet_addr(ctx_tcp->ip);
}
if (bind(new_s, (struct sockaddr *)&addr, sizeof(addr)) == -1) {
close(new_s);
return -1;
}
if (listen(new_s, nb_connection) == -1) {
close(new_s);
return -1;
}
return new_s;
}
int modbus_tcp_pi_listen(modbus_t *ctx, int nb_connection)
{
int rc;
struct addrinfo *ai_list;
struct addrinfo *ai_ptr;
struct addrinfo ai_hints;
const char *node;
const char *service;
int new_s;
modbus_tcp_pi_t *ctx_tcp_pi;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
ctx_tcp_pi = ctx->backend_data;
#ifdef OS_WIN32
if (_modbus_tcp_init_win32() == -1) {
return -1;
}
#endif
if (ctx_tcp_pi->node[0] == 0) {
node = NULL; /* == any */
} else {
node = ctx_tcp_pi->node;
}
if (ctx_tcp_pi->service[0] == 0) {
service = "502";
} else {
service = ctx_tcp_pi->service;
}
memset(&ai_hints, 0, sizeof (ai_hints));
/* If node is not NULL, than the AI_PASSIVE flag is ignored. */
ai_hints.ai_flags |= AI_PASSIVE;
#ifdef AI_ADDRCONFIG
ai_hints.ai_flags |= AI_ADDRCONFIG;
#endif
ai_hints.ai_family = AF_UNSPEC;
ai_hints.ai_socktype = SOCK_STREAM;
ai_hints.ai_addr = NULL;
ai_hints.ai_canonname = NULL;
ai_hints.ai_next = NULL;
ai_list = NULL;
rc = getaddrinfo(node, service, &ai_hints, &ai_list);
if (rc != 0) {
if (ctx->debug) {
fprintf(stderr, "Error returned by getaddrinfo: %s\n", gai_strerror(rc));
}
errno = ECONNREFUSED;
return -1;
}
new_s = -1;
for (ai_ptr = ai_list; ai_ptr != NULL; ai_ptr = ai_ptr->ai_next) {
int s;
s = socket(ai_ptr->ai_family, ai_ptr->ai_socktype,
ai_ptr->ai_protocol);
if (s < 0) {
if (ctx->debug) {
perror("socket");
}
continue;
} else {
int yes = 1;
rc = setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
(void *)&yes, sizeof (yes));
if (rc != 0) {
close(s);
if (ctx->debug) {
perror("setsockopt");
}
continue;
}
}
rc = bind(s, ai_ptr->ai_addr, ai_ptr->ai_addrlen);
if (rc != 0) {
close(s);
if (ctx->debug) {
perror("bind");
}
continue;
}
rc = listen(s, nb_connection);
if (rc != 0) {
close(s);
if (ctx->debug) {
perror("listen");
}
continue;
}
new_s = s;
break;
}
freeaddrinfo(ai_list);
if (new_s < 0) {
return -1;
}
return new_s;
}
int modbus_tcp_accept(modbus_t *ctx, int *s)
{
struct sockaddr_in addr;
socklen_t addrlen;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
addrlen = sizeof(addr);
#ifdef HAVE_ACCEPT4
/* Inherit socket flags and use accept4 call */
ctx->s = accept4(*s, (struct sockaddr *)&addr, &addrlen, SOCK_CLOEXEC);
#else
ctx->s = accept(*s, (struct sockaddr *)&addr, &addrlen);
#endif
if (ctx->s == -1) {
close(*s);
*s = -1;
return -1;
}
if (ctx->debug) {
printf("The client connection from %s is accepted\n",
inet_ntoa(addr.sin_addr));
}
return ctx->s;
}
int modbus_tcp_pi_accept(modbus_t *ctx, int *s)
{
struct sockaddr_storage addr;
socklen_t addrlen;
if (ctx == NULL) {
errno = EINVAL;
return -1;
}
addrlen = sizeof(addr);
#ifdef HAVE_ACCEPT4
/* Inherit socket flags and use accept4 call */
ctx->s = accept4(*s, (struct sockaddr *)&addr, &addrlen, SOCK_CLOEXEC);
#else
ctx->s = accept(*s, (struct sockaddr *)&addr, &addrlen);
#endif
if (ctx->s == -1) {
close(*s);
*s = -1;
}
if (ctx->debug) {
printf("The client connection is accepted.\n");
}
return ctx->s;
}
static int _modbus_tcp_select(modbus_t *ctx, fd_set *rset, struct timeval *tv, int length_to_read)
{
int s_rc;
while ((s_rc = select(ctx->s+1, rset, NULL, NULL, tv)) == -1) {
if (errno == EINTR) {
if (ctx->debug) {
fprintf(stderr, "A non blocked signal was caught\n");
}
/* Necessary after an error */
FD_ZERO(rset);
FD_SET(ctx->s, rset);
} else {
return -1;
}
}
if (s_rc == 0) {
errno = ETIMEDOUT;
return -1;
}
return s_rc;
}
static void _modbus_tcp_free(modbus_t *ctx) {
free(ctx->backend_data);
free(ctx);
}
const modbus_backend_t _modbus_tcp_backend = {
_MODBUS_BACKEND_TYPE_TCP,
_MODBUS_TCP_HEADER_LENGTH,
_MODBUS_TCP_CHECKSUM_LENGTH,
MODBUS_TCP_MAX_ADU_LENGTH,
_modbus_set_slave,
_modbus_tcp_build_request_basis,
_modbus_tcp_build_response_basis,
_modbus_tcp_prepare_response_tid,
_modbus_tcp_send_msg_pre,
_modbus_tcp_send,
_modbus_tcp_receive,
_modbus_tcp_recv,
_modbus_tcp_check_integrity,
_modbus_tcp_pre_check_confirmation,
_modbus_tcp_connect,
_modbus_tcp_close,
_modbus_tcp_flush,
_modbus_tcp_select,
_modbus_tcp_free
};
const modbus_backend_t _modbus_tcp_pi_backend = {
_MODBUS_BACKEND_TYPE_TCP,
_MODBUS_TCP_HEADER_LENGTH,
_MODBUS_TCP_CHECKSUM_LENGTH,
MODBUS_TCP_MAX_ADU_LENGTH,
_modbus_set_slave,
_modbus_tcp_build_request_basis,
_modbus_tcp_build_response_basis,
_modbus_tcp_prepare_response_tid,
_modbus_tcp_send_msg_pre,
_modbus_tcp_send,
_modbus_tcp_receive,
_modbus_tcp_recv,
_modbus_tcp_check_integrity,
_modbus_tcp_pre_check_confirmation,
_modbus_tcp_pi_connect,
_modbus_tcp_close,
_modbus_tcp_flush,
_modbus_tcp_select,
_modbus_tcp_free
};
modbus_t* modbus_new_tcp(const char *ip, int port)
{
modbus_t *ctx;
modbus_tcp_t *ctx_tcp;
size_t dest_size;
size_t ret_size;
#if defined(OS_BSD)
/* MSG_NOSIGNAL is unsupported on *BSD so we install an ignore
handler for SIGPIPE. */
struct sigaction sa;
sa.sa_handler = SIG_IGN;
if (sigaction(SIGPIPE, &sa, NULL) < 0) {
/* The debug flag can't be set here... */
fprintf(stderr, "Coud not install SIGPIPE handler.\n");
return NULL;
}
#endif
ctx = (modbus_t *)malloc(sizeof(modbus_t));
_modbus_init_common(ctx);
/* Could be changed after to reach a remote serial Modbus device */
ctx->slave = MODBUS_TCP_SLAVE;
ctx->backend = &_modbus_tcp_backend;
ctx->backend_data = (modbus_tcp_t *)malloc(sizeof(modbus_tcp_t));
ctx_tcp = (modbus_tcp_t *)ctx->backend_data;
if (ip != NULL) {
dest_size = sizeof(char) * 16;
ret_size = strlcpy(ctx_tcp->ip, ip, dest_size);
if (ret_size == 0) {
fprintf(stderr, "The IP string is empty\n");
modbus_free(ctx);
errno = EINVAL;
return NULL;
}
if (ret_size >= dest_size) {
fprintf(stderr, "The IP string has been truncated\n");
modbus_free(ctx);
errno = EINVAL;
return NULL;
}
} else {
ctx_tcp->ip[0] = '0';
}
ctx_tcp->port = port;
ctx_tcp->t_id = 0;
return ctx;
}
modbus_t* modbus_new_tcp_pi(const char *node, const char *service)
{
modbus_t *ctx;
modbus_tcp_pi_t *ctx_tcp_pi;
size_t dest_size;
size_t ret_size;
ctx = (modbus_t *)malloc(sizeof(modbus_t));
_modbus_init_common(ctx);
/* Could be changed after to reach a remote serial Modbus device */
ctx->slave = MODBUS_TCP_SLAVE;
ctx->backend = &_modbus_tcp_pi_backend;
ctx->backend_data = (modbus_tcp_pi_t *)malloc(sizeof(modbus_tcp_pi_t));
ctx_tcp_pi = (modbus_tcp_pi_t *)ctx->backend_data;
if (node == NULL) {
/* The node argument can be empty to indicate any hosts */
ctx_tcp_pi->node[0] = '0';
} else {
dest_size = sizeof(char) * _MODBUS_TCP_PI_NODE_LENGTH;
ret_size = strlcpy(ctx_tcp_pi->node, node, dest_size);
if (ret_size == 0) {
fprintf(stderr, "The node string is empty\n");
modbus_free(ctx);
errno = EINVAL;
return NULL;
}
if (ret_size >= dest_size) {
fprintf(stderr, "The node string has been truncated\n");
modbus_free(ctx);
errno = EINVAL;
return NULL;
}
}
if (service != NULL) {
dest_size = sizeof(char) * _MODBUS_TCP_PI_SERVICE_LENGTH;
ret_size = strlcpy(ctx_tcp_pi->service, service, dest_size);
} else {
/* Empty service is not allowed, error catched below. */
ret_size = 0;
}
if (ret_size == 0) {
fprintf(stderr, "The service string is empty\n");
modbus_free(ctx);
errno = EINVAL;
return NULL;
}
if (ret_size >= dest_size) {
fprintf(stderr, "The service string has been truncated\n");
modbus_free(ctx);
errno = EINVAL;
return NULL;
}
ctx_tcp_pi->t_id = 0;
return ctx;
}
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