---
title: "Arduino SERVER TCP. Send data packet struct"
url: "https://maker.wiznet.io/forum/12063"
markdown_url: "https://maker.wiznet.io/forum/12063/md"
type: "Forum topic"
category: "Ethernet Chips"
author: "svia"
created: "2016-12-21T12:24:00+09:00"
last_activity: "2017-05-04T08:39:37+09:00"
language: "en"
views: 3321
replies: 1
source: "WIZnet Makers forum (https://maker.wiznet.io/forum/)"
---

# Arduino SERVER TCP. Send data packet struct

## Question

Asked by svia on 2016-12-21 in Ethernet Chips.

Hello

I have an Arduino DUE+ IoShield A (W5500 from Wiznet). IDE 1.6. Wiznet Ethernet library

I want the Arduino to behave as a TCP Server. This server waits for a client, and sends the client an info packet.

The code is divided in two files, one the server code, and other a .h with the struct of the packet
Server.

```
#include "packet.h"
#include <Ethernet.h>


 // the media access control (ethernet hardware) address for the shield:
byte mac[] = { 0x00, 0x08, 0xDC, 0x4D, 0xD1, 0x55 };  
//the IP address for the shield:
byte ip[] = { 10, 1, 1, 3 };    
// the router's gateway address:
byte gateway[] = { 10, 1, 1, 1 };//? Esto no esun gateway, es un nodo.
// the subnet:
byte subnet[] = { 255, 255, 255, 0 };
int Port= 5000;

EthernetServer server = EthernetServer(Port);

void setup()
{
  // initialize the ethernet device
  Ethernet.begin(mac, ip, gateway, subnet);

  // start listening for clients
  server.begin();

  Info.PacketID= 0x0E;
  Info.ID_track=1;
  Info.Direction=0x00;
  Info.num=10;
  Info.stateA[0]=0x00;
  Info.stateA[1]=0x00;
  Info.stateA[2]=0x00;
  Info.stateA[3]=0x00;


void loop()
{
  // if an incoming client connects, there will be bytes available to read:
  EthernetClient client = server.available();
  if (client) {

    server.write(Info,sizeof(Info));
  }
  
}
```

packet.h

```
struct Packet{
  byte PacketID;
  byte ID_track;
  byte Direction;
  byte num;
  byte stateA[4];

};


struct Packet Info;
```

It gives error in server.write() , no matching function for call… I think that it is beacuse Info is not only an array of bytes but a struct… but I’m not sure

Any help about the server and how to send a data packet structure is welcome.
Thanks

## Replies

### Reply 1 by Kei, 2017-01-12

Hello, svia.

Arduino Library of W5500 chip is ethernet2.

In 1.6 you need to add ethernet2 directly.
From 1.8.0, however, you can add ethernet2 through the arduino library manager.

First, add / change the library.

And the write () function of the EthernetServer class has a fixed parameter type as shown below.

size_t EthernetServer::write(const uint8_t *buffer, size_t size)
[url][https://github.com/adafruit/Ethernet2/blob/master/src/EthernetServer.cpp\[/url\]](https://github.com/adafruit/Ethernet2/blob/master/src/EthernetServer.cpp%5B/url%5D)

Therefore, the custom type of the structure can not be the parameter of the function.
If you want to manage data like structs, it’s a good idea to define and manage array numbers or manage them with pointers.

Of course, if you really want to use a structure, you can use C ++ Function Overloading to change the parameters and reconstruct the function.

I hope that helps.

Best regard,
Kei

---

Source: https://maker.wiznet.io/forum/12063