How to dynamically specify TCPServer port?

General
1

I have some server code that works fine if I hardcode the listening port as a global, e.g.

TCPServer server = TCPServer(80);

but I want to be able to change that port inside the program, e.g. save the listening port in EEPROM and read it on restart.

I can't declare "TCPServer server" without the initializer, I get

QuinnsLightCPU.cpp:701:12: error: no matching function for call to 'TCPServer::TCPServer()'
TCPServer server;
^
QuinnsLightCPU.cpp:701:12: note: candidates are:
In file included from ./inc/application.h:53:0,
from Graphics.h:4,
from QuinnsLightCPU.cpp:23:
../wiring/inc/spark_wiring_tcpserver.h:42:2: note: TCPServer::TCPServer(uint16_t, network_interface_t)
TCPServer(uint16_t, network_interface_t nif=0);
^
../wiring/inc/spark_wiring_tcpserver.h:42:2: note: candidate expects 2 arguments, 0 provided
../wiring/inc/spark_wiring_tcpserver.h:34:7: note: constexpr TCPServer::TCPServer(const TCPServer&)
class TCPServer : public Print {
^
../wiring/inc/spark_wiring_tcpserver.h:34:7: note: candidate expects 1 argument, 0 provided

Is there any way to set up the server without a hardcoded port?

2

You could allocate the instance dynamically:

TCPServer* server = NULL;

void setup()
{
   int port;
   EEPROM.get(0, port);
   server = new TCPServer(port);
}

It’s like this because of compatibility with arduino, although in future, I see no issue with adding an optional port to the “begin” method. Then the code could be simpler:

TCPServer server;

void setup()
{
    int port;
    EEPROM.get(0, port);
    server.begin(port);
}
4 Likes
3

Thanks for the idea. As written this global declaration

TCPServer server = NULL;

gives this:

QuinnsLightCPU.cpp:56:20: warning: passing NULL to non-pointer argument 1 of 'TCPServer::TCPServer(uint16_t, network_int
erface_t)' [-Wconversion-null]
TCPServer server = NULL;
^

and this in setup()

server = new TCPServer(wsPort);

gives this

QuinnsLightCPU.cpp: In function 'void setup()':
QuinnsLightCPU.cpp:610:9: error: invalid user-defined conversion from 'TCPServer*' to 'const TCPServer&' [-fpermissive]
server = new TCPServer(wsPort);
^
In file included from ./inc/application.h:53:0,
from Graphics.h:4,
from QuinnsLightCPU.cpp:23:
../wiring/inc/spark_wiring_tcpserver.h:42:2: note: candidate is: TCPServer::TCPServer(uint16_t, network_interface_t)
TCPServer(uint16_t, network_interface_t nif=0);
^
../wiring/inc/spark_wiring_tcpserver.h:42:2: note: no known conversion for argument 1 from 'TCPServer*' to 'uint16_t {
aka short unsigned int}'
QuinnsLightCPU.cpp:610:9: error: invalid conversion from 'TCPServer*' to 'uint16_t {aka short unsigned int}' [-fpermissi
ve]
server = new TCPServer(wsPort);
^
In file included from ./inc/application.h:53:0,
from Graphics.h:4,
from QuinnsLightCPU.cpp:23:
../wiring/inc/spark_wiring_tcpserver.h:42:2: error: initializing argument 1 of 'TCPServer::TCPServer(uint16_t, network
_interface_t)' [-fpermissive]
TCPServer(uint16_t, network_interface_t nif=0);
^

But if I remove the "new" from the assignment in setup() the code will compile and it looks like it's working as expected so I'll ignore that warning for now.

Thanks again.

4

Then the code could be simpler

A single fixed port number is not so hot, to understate.

Rather than New which is off the heap, declaring a static class instance at compile time is probably prudent. Static outside a function, and/or global, rather than off the stack as a local.

5

There was a typo - I changed TCPServer to TCPServer*.