Need to clone modbus_t TCP context

[Fred-Spreen-Logikos]

In order to create a multi-threaded TCP server, it is necessary to duplicate the modbus_t TCP context, but no function currently exists to do this. Additionally, the modbus_t structure points to connection-specific data, so a simple memcpy() doesn't do the job.

Below is a patch which provides the appropriate functions.

diff -r a/libmodbus/src/modbus-tcp.c b/libmodbus/src/modbus-tcp.c --- a/libmodbus/src/modbus-tcp.c +++ b/libmodbus/src/modbus-tcp.c @@ -732,3 +732,19 @@

 return ctx;

} + +void modbus_clone_tcp(modbus_t* new_ctx, modbus_t* ctx) +{

• new_ctx = (modbus_t *) malloc(sizeof(modbus_t));
• memcpy(new_ctx, ctx, sizeof(modbus_t));
• new_ctx->backend_data = (modbus_tcp_t *) malloc(sizeof(modbus_tcp_t));
• memcpy(new_ctx->backend_data, ctx->backend_data, sizeof(modbus_tcp_t)); +} + +void modbus_clone_tcp_pi(modbus_t* new_ctx, modbus_t* ctx) +{
• new_ctx = (modbus_t *) malloc(sizeof(modbus_t));
• memcpy(new_ctx, ctx, sizeof(modbus_t));
• new_ctx->backend_data = (modbus_tcp_pi_t *) malloc(sizeof(modbus_tcp_pi_t));

• memcpy(new_ctx->backend_data, ctx->backend_data, sizeof(modbus_tcp_pi_t)); +} diff -r a/libmodbus/src/modbus-tcp.h b/libmodbus/src/modbus-tcp.h --- a/libmodbus/src/modbus-tcp.h +++ b/libmodbus/src/modbus-tcp.h @@ -41,9 +41,11 @@ modbus_t* modbus_new_tcp(const char ip_address, int port); int modbus_tcp_listen(modbus_t ctx, int nb_connection); int modbus_tcp_accept(modbus_t ctx, int socket); +void modbus_clone_tcp(modbus_t new_ctx, modbus_t ctx);

  modbus_t* modbus_new_tcp_pi(const char node, const char service); int modbus_tcp_pi_listen(modbus_t ctx, int nb_connection); int modbus_tcp_pi_accept(modbus_t ctx, int socket); +void modbus_clone_tcp_pi(modbus_t new_ctx, modbus_t *ctx);

  endif /* _MODBUS_TCPH */

[stephane]

Once you've copied the structure it doesn't allow you to share the same socket between your threads. Could you explain your use case?

[stephane]

No answer...