TCP:用户只需要提供待发数据的起始地址和长度,内核会根据实际情况封装在合适大小的数据包中。UDP:需要用户自行将数据封装在netbuf结构中。 netbuf数据结构:/** "Network buffer" - contains data and addressing info */ struct netbuf { struct pbuf *p, *ptr; /* 包缓冲区。p:pbuf链。ptr:pbuf链...
The focus of the lwIP TCP/IP implementation is to reduce resource usage while still having a full scale TCP. This makes lwIP suitable for use in embedded systems with tens of kilobytes of free RAM and room for around 40 kilobytes of code ROM. Main features include: –Protocols: IP, ICMP,...
这里的区别就是新建了send和recv的结构体,里面存放了缓冲的buf和size大小;lwip_demo中需要建立一个link_socjet_info结构体的指针socket_info,然后mem_malloc分配socket_info的内存;之后调用socket建立连接,通过setsockopt设置optval选项值;然后配置socket_info的IP协议、端口号还有本地IP地址,需要注意这里是广播所以配置为...
TCP-based protocol (ported to mbedTLS) (see changelog for more info) * PPPoS and PPPoE (Point-to-point protocol over Serial/Ethernet) * DNS (Domain name resolver incl. mDNS) * 6LoWPAN (via IEEE 802.15.4, BLE or ZEP) APPLICATIONS * HTTP server with SSI and CGI (HTTPS via altcp) * ...
因为tcp_receive函数在收到数据后,会把窗口缩小,表示接收数据的空间被刚收到的数据占用了,所以你在tcp_receive中可以看到这样的语句, pcb->rcv_wnd -= tcplen; pcb->rcv_wnd -= TCP_TCPLEN(cseg); 故而,在应用层处理完这些数据后,要通知LWIP,这些空间可以恢复到原来大小了,那些数据已经用过了。
tcpip_thread: CALLBACK 0041c5bc LOG_INFO:pppInput[0]: ip in pbuf len=40 TCP header: +---+ | 5000 | 4097 | (src port, dest port) +---+ | -1374915893 | (seq no) +---+ | 0000006950 | (ack no) +---+ | 5 | |
(last changed: June 16, 2011) lwip_init() must be called before any tcp functions are called. void tcp_tmr(void) After lwip_init() is called, you must call tcp_tmr() every TCP_TMR_INTERVAL milliseconds (default is 250 milliseconds). However, since some t
;39tcp_write(pcb, LOGIN_INFO, strlen(LOGIN_INFO),1);4041returnERR_OK;42} 在这个函数中,我们实现的功能主要是三方面:注册Telnet服务器消息处理回调函数;注册Telnet服务器连接错误回调函数;初始化Telnet服务器的状态。这个初始化是在连接建立后,Telnet服务器与客户端的交互初始化,比如登录状态,用户提示等。
你傻啊,keepalive是保持活动的意思。意思就是说,不要关闭tcp。为了实现这项功能,带有keepalive的TCP,...