所以我在互联网上找不到任何简单的例子，而不是echolaze和lwip的echo程序，这对我来说很好，这里是他们的文件： echo.c：
/*
* Copyright (c) 2009 Xilinx, Inc. All rights reserved.
*
* Xilinx, Inc.
* XILINX IS PROVIDING THIS DESIGN, CODE, OR INFORMATION "AS IS" AS A
* COURTESY TO YOU. BY PROVIDING THIS DESIGN, CODE, OR INFORMATION AS
* ONE POSSIBLE IMPLEMENTATION OF THIS FEATURE, APPLICATION OR
* STANDARD, XILINX IS MAKING NO REPRESENTATION THAT THIS IMPLEMENTATION
* IS FREE FROM ANY CLAIMS OF INFRINGEMENT, AND YOU ARE RESPONSIBLE
* FOR OBTAINING ANY RIGHTS YOU MAY REQUIRE FOR YOUR IMPLEMENTATION.
* XILINX EXPRESSLY DISCLAIMS ANY WARRANTY WHATSOEVER WITH RESPECT TO
* THE ADEQUACY OF THE IMPLEMENTATION, INCLUDING BUT NOT LIMITED TO
* ANY WARRANTIES OR REPRESENTATIONS THAT THIS IMPLEMENTATION IS FREE
* FROM CLAIMS OF INFRINGEMENT, IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE.
*
*/
#include <stdio.h>
#include <string.h>
#include "lwip/err.h"
#include "lwip/tcp.h"
int transfer_data() {
return 0;
}
void print_app_header()
{
xil_printf("\n\r\n\r-----lwIP TCP echo server ------\n\r");
xil_printf("TCP packets sent to port 6001 will be echoed back\n\r");
}
err_t recv_callback(void *arg, struct tcp_pcb *tpcb,
struct pbuf *p, err_t err)
{
/* do not read the packet if we are not in ESTABLISHED state */
if (!p) {
tcp_close(tpcb);
tcp_recv(tpcb, NULL);
return ERR_OK;
}
/* indicate that the packet has been received */
tcp_recved(tpcb, p->len);
/* echo back the payload */
/* in this case, we assume that the payload is < TCP_SND_BUF */
if (tcp_sndbuf(tpcb) > p->len) {
err = tcp_write(tpcb, p->payload, p->len, 1);
} else
print("no space in tcp_sndbuf\n\r");
/* free the received pbuf */
pbuf_free(p);
return ERR_OK;
}
err_t accept_callback(void *arg, struct tcp_pcb *newpcb, err_t err)
{
static int connection = 1;
/* set the receive callback for this connection */
tcp_recv(newpcb, recv_callback);
/* just use an integer number indicating the connection id as the
callback argument */
tcp_arg(newpcb, (void*)connection);
/* increment for subsequent accepted connections */
connection++;
return ERR_OK;
}
int start_application()
{
struct tcp_pcb *pcb;
err_t err;
unsigned port = 7;
/* create new TCP PCB structure */
pcb = tcp_new();
if (!pcb) {
xil_printf("Error creating PCB. Out of Memory\n\r");
return -1;
}
/* bind to specified @port */
err = tcp_bind(pcb, IP_ADDR_ANY, port);
if (err != ERR_OK) {
xil_printf("Unable to bind to port %d: err = %d\n\r", port, err);
return -2;
}
/* we do not need any arguments to callback functions */
tcp_arg(pcb, NULL);
/* listen for connections */
pcb = tcp_listen(pcb);
if (!pcb) {
xil_printf("Out of memory while tcp_listen\n\r");
return -3;
}
/* specify callback to use for incoming connections */
tcp_accept(pcb, accept_callback);
xil_printf("TCP echo server started @ port %d\n\r", port);
return 0;
}
这是main.c：
/*
* Copyright (c) 2009-2010 Xilinx, Inc. All rights reserved.
*
* Xilinx, Inc.
* XILINX IS PROVIDING THIS DESIGN, CODE, OR INFORMATION "AS IS" AS A
* COURTESY TO YOU. BY PROVIDING THIS DESIGN, CODE, OR INFORMATION AS
* ONE POSSIBLE IMPLEMENTATION OF THIS FEATURE, APPLICATION OR
* STANDARD, XILINX IS MAKING NO REPRESENTATION THAT THIS IMPLEMENTATION
* IS FREE FROM ANY CLAIMS OF INFRINGEMENT, AND YOU ARE RESPONSIBLE
* FOR OBTAINING ANY RIGHTS YOU MAY REQUIRE FOR YOUR IMPLEMENTATION.
* XILINX EXPRESSLY DISCLAIMS ANY WARRANTY WHATSOEVER WITH RESPECT TO
* THE ADEQUACY OF THE IMPLEMENTATION, INCLUDING BUT NOT LIMITED TO
* ANY WARRANTIES OR REPRESENTATIONS THAT THIS IMPLEMENTATION IS FREE
* FROM CLAIMS OF INFRINGEMENT, IMPLIED WARRANTIES OF MERCHANTABILITY
* AND FITNESS FOR A PARTICULAR PURPOSE.
*
*/
#include <stdio.h>
#include "xparameters.h"
#include "netif/xadapter.h"
#include "platform.h"
#include "platform_config.h"
/* defined by each RAW mode application */
void print_app_header();
int start_application();
int transfer_data();
/* missing declaration in lwIP */
void lwip_init();
void
print_ip(char *msg, struct ip_addr *ip)
{
print(msg);
xil_printf("%d.%d.%d.%d\n\r", ip4_addr1(ip), ip4_addr2(ip),
ip4_addr3(ip), ip4_addr4(ip));
}
void
print_ip_settings(struct ip_addr *ip, struct ip_addr *mask, struct ip_addr *gw)
{
print_ip("Board IP: ", ip);
print_ip("Netmask : ", mask);
print_ip("Gateway : ", gw);
}
int main()
{
struct netif *netif, server_netif;
struct ip_addr ipaddr, netmask, gw;
/* the mac address of the board. this should be unique per board */
unsigned char mac_ethernet_address[] = { 0x00, 0x0a, 0x35, 0x00, 0x01, 0x02 };
netif = &server_netif;
init_platform();
/* initliaze IP addresses to be used */
IP4_ADDR(&ipaddr, 192, 168, 1, 10);
IP4_ADDR(&netmask, 255, 255, 255, 0);
IP4_ADDR(&gw, 192, 168, 1, 1);
print_app_header();
print_ip_settings(&ipaddr, &netmask, &gw);
lwip_init();
/* Add network interface to the netif_list, and set it as default */
if (!xemac_add(netif, &ipaddr, &netmask, &gw, mac_ethernet_address, PLATFORM_EMAC_BASEADDR)) {
xil_printf("Error adding N/W interface\n\r");
return -1;
}
netif_set_default(netif);
/* Create a new DHCP client for this interface.
* Note: you must call dhcp_fine_tmr() and dhcp_coarse_tmr() at
* the predefined regular intervals after starting the client.
*/
/* dhcp_start(netif); */
/* now enable interrupts */
platform_enable_interrupts();
/* specify that the network if is up */
netif_set_up(netif);
/* start the application (web server, rxtest, txtest, etc..) */
start_application();
/* receive and process packets */
while (1) {
xemacif_input(netif);
tcp_write()
//transfer_data();
}
/* never reached */
cleanup_platform();
return 0;
}
现在我根本无法理解这段代码（其中一些但不是全部）你们可以告诉我如何更改这段代码，而不是回显相同的数据，它会发送回主机一个包含“嘿”的字符串。 谢谢你
答案 0 :(得分：2)
这一行
err = tcp_write(tpcb, p->payload, p->len, 1);
从rescive数据p发回数据（p->有效负载 - 传入消息） 改变它，比如
err = tcp_write(tpcb, "hey", 3, 1);