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计算机网络滑动窗口实验程序清单 Page 4/4#include #include #include protocol.h#include datalink.hstatic int phy_ready = 0;/物理层状态static boolean between (seq_nr a,seq_nr b,seq_nr c)if( (a=b)&(bc) | (ca)&(a=b) | (bc)&(c 1; used for outbound stream, and initianize next frame going out */seq_nr ack_expected=0; /* oldest frame as yet unacknowledged, and initianize next ack expected inbound */seq_nr frame_expected=0; /* next frame expected on inbound stream, and initialize number of frame expected inbound */frame r; /* scratch varible */packet bufferMAX_SEQ+1; /* buffers for the outbound stream */seq_nr nbuffered=0; /* # output buffers currently in use, and initially no packets are buffered */seq_nr i; /* used to index into the buffer array */ protocol_init(argc, argv);lprintf(nDesigned by Liu Yang,Teng Xiao,Xu Ye Nan, build: _DATE_ _TIME_n);enable_network_layer();while(true)event = wait_for_event(&arg);switch(event)case NETWORK_LAYER_READY: /* the network layer has a packet to send */bufferLennext_frame_to_send = get_packet(buffernext_frame_to_send);/*bufferLen 存储每个buffer中数据的有效长度*/nbuffered +;/* expand the senders window */send_data(Data,next_frame_to_send,frame_expected,buffer,bufferLen); /发送数据帧inc(next_frame_to_send);/* advance senders upper window edge */break;case PHYSICAL_LAYER_READY:phy_ready = 1;break;case FRAME_RECEIVED:/* a data or control frame has arrived */len = recv_frame(unsigned char *) &r,sizeof(r);/返回存放帧的缓冲区的大小if (len 6 | crc32(unsigned char *)&r, len) != 0) /大小不够或者校验错误 dbg_event(* Receiver Error, Bad CRC Checksumn);if(r.seq = frame_expected)/若错误帧中的seq是期望的seq，则发送nak(忽略seq是错误的情况)send_data(Nak,next_frame_to_send,frame_expected,buffer,bufferLen);break; if(r.kind = Data)/接收的是数据帧dbg_frame(Recv data %d %d, ID %dn,r.seq,r.ack,*(short *));if(r.seq = frame_expected)/若所得帧是期望得到的帧，递交给网络层put_packet(,len-7);start_ack_timer(ACK_TIMER);inc(frame_expected);else if(r.kind = Ack)/接受ackdbg_frame(Recv ACK %dn, r.ack);else/接受nak，r.ack为对方需要重传的窗口号，表明对方已经收到r.ack之前的数据帧/即相当于收到了一个窗口号为r.ack-1的ackdbg_frame(Recv NAK %dn, r.ack);next_frame_to_send = r.ack;r.ack = (r.ack+MAX_SEQ) % (MAX_SEQ+1);while(between(ack_expected,r.ack,next_frame_to_send)/执行收到了ack的操作nbuffered -;stop_timer(ack_expected);inc(ack_expected);for(i=1;i=nbuffered;i+)/重发错误帧send_data(Data,next_frame_to_send,frame_expected,buffer,bufferLen);inc(next_frame_to_send);break;while(between(ack_expected,r.ack,next_frame_to_send)nbuffered -;stop_timer(ack_expected);inc(ack_expected);break;case DATA_TIMEOUT:/数据发送超时 重发dbg_event(- data %d timeoutn, arg);next_frame_to_send = ack_expected;for(i=1;i=nbuffered;i+)send_data(Data,next_frame_to_send,frame_expected,buffer,bufferLen);inc(next_frame_to_send);break;case ACK_TIMEOUT:/ack超时 单独发送ack帧send_data(Ack,next_frame_to