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Use libmodbus to decode incoming Modbus TCP messages #254

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Use libmodbus to decode incoming Modbus TCP messages #254

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50 changes: 39 additions & 11 deletions webserver/core/server.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -29,6 +29,7 @@
#include <string.h>
#include <pthread.h>
#include <fcntl.h>
#include <modbus.h>

#include "ladder.h"

Expand Down Expand Up @@ -180,15 +181,27 @@ int listenToClient(int client_fd, unsigned char *buffer)
//-----------------------------------------------------------------------------
void processMessage(unsigned char *buffer, int bufferSize, int client_fd, int protocol_type)
{
int messageSize = 0;
if (protocol_type == MODBUS_PROTOCOL)
{
int messageSize = processModbusMessage(buffer, bufferSize);
write(client_fd, buffer, messageSize);
messageSize = processModbusMessage(buffer, bufferSize);
}
else if (protocol_type == ENIP_PROTOCOL)
{
int messageSize = processEnipMessage(buffer, bufferSize);
write(client_fd, buffer, messageSize);
messageSize = processEnipMessage(buffer, bufferSize);
}
while (messageSize > 0)
{
ssize_t bytesWritten = write(client_fd, buffer, messageSize);
if (bytesWritten < 0)
{
char log_msg[1000];
sprintf(log_msg, "Server: Error writing response: %zd\n", bytesWritten);
log(log_msg);
break;
}
buffer += bytesWritten;
messageSize -= bytesWritten;
}
}

Expand All @@ -201,24 +214,34 @@ void *handleConnections(void *arguments)
int *args = (int *)arguments;
int client_fd = args[0];
int protocol_type = args[1];
static_assert(NET_BUFFER_SIZE >= MODBUS_TCP_MAX_ADU_LENGTH);
unsigned char buffer[NET_BUFFER_SIZE];
int messageSize;
bool *run_server;

modbus_t *ctx = NULL;

if (protocol_type == MODBUS_PROTOCOL)
{
run_server = &run_modbus;
ctx = modbus_new_tcp(NULL, 502); // The IP and port don't matter
modbus_set_socket(ctx, client_fd);
}
else if (protocol_type == ENIP_PROTOCOL)
run_server = &run_enip;

sprintf(log_msg, "Server: Thread created for client ID: %d\n", client_fd);
log(log_msg);

while(*run_server)
while (*run_server)
{
//unsigned char buffer[NET_BUFFER_SIZE];
//int messageSize;

messageSize = listenToClient(client_fd, buffer);
if (protocol_type == MODBUS_PROTOCOL)
{
messageSize = modbus_receive(ctx, buffer);
}
else
{
messageSize = listenToClient(client_fd, buffer);
}
if (messageSize <= 0 || messageSize > NET_BUFFER_SIZE)
{
// something has gone wrong or the client has closed connection
Expand All @@ -237,10 +260,15 @@ void *handleConnections(void *arguments)

processMessage(buffer, messageSize, client_fd, protocol_type);
}
//printf("Debug: Closing client socket and calling pthread_exit in server.cpp\n");
// printf("Debug: Closing client socket and calling pthread_exit in server.cpp\n");
close(client_fd);
sprintf(log_msg, "Terminating Modbus connections thread\r\n");
log(log_msg);
if (ctx != NULL)
{
modbus_close(ctx);
modbus_free(ctx);
}
pthread_exit(NULL);
}

Expand Down