File content as of revision 3:30b262b6c2f9:

#include "mbed.h"
#include "EthernetInterface.h"

#define DHCP 1

uint8_t mac_addr[6] = {0x00, 0x08, 0xdc, 0x12, 0x34, 0x45};
const char ip_addr[] = "xxx.xxx.xxx.xxx"; 
const char mask_addr[] = "xxx.xxx.xxx.xxx"; 
const char gateway_addr[] = "xxx.xxx.xxx.xxx"; 

const char* Target_addr = "192.168.0.2";
const int Target_port = 10000;
char* test=NULL;

SPISlave slave(PA_8, PA_7, PA_6, PA_5); // mosi, miso, sclk, ssel
 
int main() {

    char txbuf[256]={0,};
    char rxbuf[256]={0,};
    int i, n, close_cnt, length, send_flag=0, cnt_flag=0, send_cnt=0;
    int slave_h=0;

    printf("SPI to Ethernet Slave\r\n");
  
    /*
    * SPI Setting
    */
    slave.format(8,3);
    slave.frequency(1000000);
    /*
    * Network Setting
    */
    printf("Wait a second...\r\n");
    EthernetInterface eth;
    #if DHCP==1
        printf("Network Setting DHCP\r\n");
        eth.init(mac_addr); 
    #else
        printf("Network Setting Static\r\n");
        eth.init(mac_addr, ip_addr, mask_addr, gateway_addr);
    #endif
    eth.connect();
    printf("IP Address is %s\r\n", eth.getIPAddress());
    while(1) 
    { 
        printf("Check Ethernet Link\r\n");
        if(eth.link() == true)
        {
            printf("Link up\r\n");
            break;
        }
    }
    
    /*
    * Create Client Socket and Connecting
    */
    TCPSocketConnection socket;
    while(1)
    {       
        while (socket.connect(Target_addr, Target_port) < 0) 
        {
            printf("Unable to connect to (%s) on port (%d)\r\n", Target_addr, Target_port);
            wait(1);
        }
        printf("Connected to Server at %s\r\n",Target_addr);
        
        while(1)
        {
            n = socket.receive(txbuf, sizeof(txbuf));
            printf("n = %d\r\n", n);
            if(slave.receive())
            {
                slave_h = slave.read();
                printf("slave_h = char:%c, dec:%d, hex:%x\r\n", slave_h, slave_h, slave_h);
                
                if(slave_h==0x55)
                {
                    printf("check loop slave_h if\r\n");
                    if(n > 0)
                    {
                        printf("check loop n if\r\n");
                        slave.reply(0x55);
                        cnt_flag = 1;
                    }
                    else
                    {
                        slave.reply(0x00);
                    }
                }
                else if((slave_h==0x01)&&(cnt_flag==1))   
                {
                    printf("check loop slave_h + cnt_flag if\r\n");
                    slave.reply(n);
                    cnt_flag = 0;
                    send_flag = 1;
                }
                else
                {
                    printf("else\r\n");
                    test = (char*)slave_h;
                    socket.send(test, 1);
                } 
                
                if(send_flag)
                {
                    printf("send_flag\r\n");
                    slave.reply(txbuf[send_cnt]);
                    send_cnt++;
                    printf("send_cnt = char:%c, dec:%d, hex:%x\r\n", send_cnt, send_cnt, send_cnt);
                    if(send_cnt==n)
                    {
                           printf("send_cnt\r\n");
                           send_cnt=0;
                           send_flag=0;      
                    }
                }      
            }
        }
    }
}