文件传输协议的(C语言)实现

课程设计：FTP的设计与实现一、目的Internet提供了很多类型的网络服务，这些服务实际上都是应用层的服务。

FTP服务是基于TCP协议的网络服务。

文件传送是各种计算机网络都实现的基本功能，文件传送协议是一种最基本的应用层协议。

通过完成一个文件传送协议FTP的实现，学会利用已有网络环境设计并实现简单应用层协议，掌握TCP/IP网络应用程序基本的设计方法和实现技巧。

二、内容和要求每两人一组，分别实现FTP协议客户端程序和服务器程序。

客户端程序具有文件列表、下载文件、上传文件等常用功能。

服务器程序支持改变工作目录、文件列表、下载文件等常用的服务。

因为FTP协议比较复杂，为了简单起见，客户端只实现FTP客户端协议的一个子集，总的来说有以下几个功能：●连接到指定的FTP服务器；●断开和主机的连接；●进入子目录；●退出子目录；●列出服务器当前目录下的所有文件●从服务器下载指定的文件到本地(可以同时指定多个文件连续下载)●从本地上传指定的文件到服务器实现以上几个功能时会涉及到下面的几个FTP命令：●USER username●PASS password●CWD directory-name●PORT host-port●TYPE A or I●RETR filename●STOR filename●LIST directory用户界面应该能够为程序输入下面的信息：●服务器主机名●用户名、口令●数据的传送类型●要进入的服务器目录●要下载的远程文件名●要上载的本地文件名和远程文件名同时，界面也为用户输出以下的信息：●FTP服务器上的文件和目录列表●从服务器返回的应答使用Socket进行Client/Server程序设计的一般连接过程是这样的：Server端Listen(监听)某个端口是否有连接请求，Client端向Server端发出Connect(连接)请求，Server端向Client端发回Accept（接受）消息。

一个连接就建立起来了。

Server端和Client端都可以通过Send，Write等方法与对方通信。

对于一个功能齐全的Socket，都要包含以下基本结构，其工作过程包含以下四个基本的步骤：（1）创建Socket；（2）打开连接到Socket的输入/出流；（3）按照一定的协议对Socket进行读/写操作；（4）关闭Socket.第三步是程序员用来调用Socket和实现程序功能的关键步骤，其他三步在各种程序中基本相同。

/****************client.c****************/#include <winsock2.h>#include <stdio.h>#include <stdlib.h>#pragma comment(lib,"ws2_32.lib")#define DEFAULT_PORT 2302#define DEFAULT_BUFFER 2048#define DEFAULT_MESSAGE "This is a test of the emergency \ broadcasting system"char szServerip[128], // Server to connect toszMessage[1024]; // Message to send to severint iPort = DEFAULT_PORT; // Port on server to connect to//DWORD dwCount = DEFAULT_COUNT; // Number of times to send messageBOOL bSendOnly = FALSE; // Send data only; don't receiveint dirfun();int getfun();int putfun();int pwdfun();int cdfun();int mdfun();int delfun();int usafun();void usage(){printf("usage: client [-p:x] [-s:IP] [-n:x] [-o]\n\n");printf(" -p:x Remote port to send to\n");printf(" -s:IP Server's IP address or hostname\n");printf(" -n:x Number of times to send message\n");printf(" -o Send messages only; don't receive\n");ExitProcess(1);}void ValidateArgs(int argc, char **argv){int i;for(i = 1; i < argc; i++){if ((argv[i][0] == '-') || (argv[i][0] == '/')){switch (tolower(argv[i][1])){case 'p': // Remote portif (strlen(argv[i]) > 3)iPort = atoi(&argv[i][3]);break;case 's': // Serverif (strlen(argv[i]) > 3)strcpy(szServerip, &argv[i][3]);break;case 'n': // Number of times to send messageif (strlen(argv[i]) > 3)//dwCount = atol(&argv[i][3]);break;case 'o': // Only send message; don't receivebSendOnly = TRUE;break;default:usage();break;}}}}int main(int argc, char **argv){WSADATA wsd;SOCKET sClient;char szBuffer[DEFAULT_BUFFER];int ret;//unsigned int i;//int j;struct sockaddr_in server;struct hostent *host = NULL;char choice[5],choice2[40];// Parse the command line and load Winsock//argv[1]="-s:127.0.0.1";strcpy(szServerip, &argv[1][3]);//ValidateArgs(argc, argv);if (WSAStartup(MAKEWORD(2,2), &wsd) != 0){printf("Failed to load Winsock library!\n");return 1;}//strcpy(szMessage, DEFAULT_MESSAGE);//// Create the socket, and attempt to connect to the server//sClient = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);if (sClient == INVALID_SOCKET){printf("socket() failed: %d\n", WSAGetLastError());return 1;}server.sin_family = AF_INET;server.sin_port = htons(iPort);printf("server.sin_port=%u\n",server.sin_port);server.sin_addr.s_addr = inet_addr(szServerip);//// If the supplied server address wasn't in the form// "c.ddd" it's a hostname, so try to resolve it//if (server.sin_addr.s_addr == INADDR_NONE){host = gethostbyname(szServerip);if (host == NULL){printf("Unable to resolve server: %s\n", szServerip);return 1;}CopyMemory(&server.sin_addr, host->h_addr_list[0],host->h_length);}if (connect(sClient, (struct sockaddr *)&server,sizeof(server)) == SOCKET_ERROR){printf("connect() failed: %d\n", WSAGetLastError());return 1;}//显示接通信息//////for(j=0;j<2;j++)//{ret = recv(sClient, szBuffer, DEFAULT_BUFFER, 0);if (ret == 0) // Graceful closereturn 0;else if (ret == SOCKET_ERROR){printf("recv() failed: %d\n", WSAGetLastError());return 0;}szBuffer[ret] = '\0';printf("%s\n",szBuffer);if(ret<15){ret = recv(sClient, szBuffer, DEFAULT_BUFFER, 0);if (ret == 0) // Graceful closereturn 0;else if (ret == SOCKET_ERROR){//printf("recv() failed: %d\n", WSAGetLastError());return 0;}szBuffer[ret] = '\0';printf("%s\n",szBuffer);}//printf("DEFAULT_BUFFER=%d\n",DEFAULT_BUFFER);}while(1){puts("------------------------------------------");printf("ftp> ");scanf("%s", choice);if(strncmp(choice,"dir",3)==0||strncmp(choice,"DIR",2)==0){dirfun(sClient);continue;}else if(strncmp(choice,"pwd",3)==0||strncmp(choice,"PWD",3)==0) {pwdfun(sClient);continue;}else if(strncmp(choice,"?",1)==0){usafun(sClient);continue;}else if(strncmp(choice,"quit",4)==0||strncmp(choice,"QUIT",2)==0) {break;}scanf("%s", choice2);if(strncmp(choice,"get",3)==0||strncmp(choice,"GET",3)==0){getfun(sClient,choice2);continue;}else if(strncmp(choice,"put",3)==0||strncmp(choice,"PUT",3)==0) {putfun(sClient,choice2);continue;}else if(strncmp(choice,"cd",2)==0||strncmp(choice,"CD",2)==0){cdfun(sClient,choice2);continue;}else if(strncmp(choice,"md",2)==0||strncmp(choice,"MD",2)==0){mdfun(sClient,choice2);continue;}else if(strncmp(choice,"del",3)==0||strncmp(choice,"DEL",3)==0){delfun(sClient,choice2);continue;}//elseputs("输入错误，请重新输入");fflush(stdin);fflush(stdin);printf("\n");printf("\n");}closesocket(sClient);WSACleanup();return 0;}int dirfun(SOCKET sClient){int ret;char *MSG="dir$";char szBuffer[80];strcpy(szMessage, MSG);ret = send(sClient, szMessage, strlen(szMessage), 0);if (ret == 0)return 1;else if (ret == SOCKET_ERROR){printf("send() failed: %d\n", WSAGetLastError());return 1;}//printf("Send %d bytes\n", ret);//printf("bSendOnly=%d\n",bSendOnly);while(!bSendOnly){//读取流并显示//ret = recv(sClient, szBuffer, 80, 0);//printf("%s",szBuffer);ret = recv(sClient, szBuffer, 80, 0);if (ret == 0) // Graceful closereturn 1;else if (ret == SOCKET_ERROR){printf("recv() failed: %d\n", WSAGetLastError());return 1;}szBuffer[ret] = '\0';if(strncmp(szBuffer,"226 Close",strlen("226 Close"))==0){break;}printf("%s",szBuffer);if(strncmp(szBuffer,"500 Syntax error",strlen("500 Syntax error"))==0){break;}}return 0;}int getfun(SOCKET sClient,char filename[40]){int ret;FILE *fpre;char szBuffer[80];szMessage[0]='\0';strcat(szMessage, "get$");//strcat(szMessage, "\\");strcat(szMessage,filename);//printf("MSG[4]=%c\n",szMessage[4]);//szMessage[0]='g';szMessage[1]='e';szMessage[2]='t';////szMessage[4]='m';szMessage[5]='e';szMessage[6]='.';szMessage[7]='t';////szMessage[8]='x';szMessage[9]='t';szMessage[10]='\0';ret = send(sClient, szMessage, strlen(szMessage)+1, 0);if (ret == 0)return 1;else if (ret == SOCKET_ERROR){printf("send() failed: %d\n", WSAGetLastError());return 1;}printf("Send %d bytes\n", ret);ret = recv(sClient, szBuffer, 80, 0);/*if (ret == 0) // Graceful closebreak;else if (ret == SOCKET_ERROR){printf("recv() failed: %d\n", WSAGetLastError());break;}*/szBuffer[ret] = '\0';printf("%s\n",szBuffer);if(strncmp( szBuffer,"125 Transfering...",strlen("125 Transfering...") )==0) {if( (fpre=fopen(filename,"w")) == NULL ){printf("open errer");return 1;}printf("bSendOnly=%d\n",bSendOnly);while(!bSendOnly){//读取流并显示ret = recv(sClient, szBuffer, 80, 0);if (ret == 0) // Graceful closereturn 1;else if (ret == SOCKET_ERROR){printf("recv() failed: %d\n", WSAGetLastError());return 1;}szBuffer[ret] = '\0';//printf("%s",szBuffer);if(strncmp(szBuffer,"226 Transfer",strlen("226 Transfer"))==0){break;}if(strncmp(szBuffer,"500 Syntax error",strlen("500 Syntax error"))==0){break;}fprintf(fpre,"%s",szBuffer);}printf("%s\n",szBuffer);fclose(fpre);}return 0;}int putfun(SOCKET sClient,char filename[40]){int ret;//int i;FILE *fpse;//char *filename;//char *MSG="get\0me.txt";char szBuffer[80],temp_buffer[80];//sprintf(szMessage, "get\0","te.txt\0");szMessage[0]='\0';strcat(szMessage, "put$");strcat(szMessage,filename);ret = send(sClient, szMessage, strlen(szMessage)+1, 0);if (ret == 0)return 0;else if (ret == SOCKET_ERROR){printf("send() failed: %d\n", WSAGetLastError());return 1;}//printf("Send %d bytes\n", ret);//filename="me.txt";printf("filename=%s\n",filename);if( (fpse=fopen(filename,"r")) == NULL ){printf("open errer");return 1;}else{printf("The file %s found,ready to transfer.\n",filename);//i=0;while (fgets(temp_buffer,80,fpse)!=NULL){sprintf(szBuffer,"%s",temp_buffer);send(sClient, szBuffer, 80, 0);}}sprintf(szBuffer, "226 Transfer completed... \r\n");ret = send(sClient, szBuffer, strlen(szBuffer), 0);fclose(fpse);return 0;}int pwdfun(SOCKET sClient){int ret;char *MSG="pwd$";char szBuffer[160];strcpy(szMessage, MSG);ret = send(sClient, szMessage, strlen(szMessage), 0);if (ret == 0)return 1;else if (ret == SOCKET_ERROR){printf("send() failed: %d\n", WSAGetLastError());return 1;}printf("Send %d bytes\n", ret);printf("bSendOnly=%d\n",bSendOnly);while(!bSendOnly){//读取流并显示ret = recv(sClient, szBuffer, 160, 0);if (ret == 0) // Graceful closereturn 1;else if (ret == SOCKET_ERROR){printf("recv() failed: %d\n", WSAGetLastError());return 1;}szBuffer[ret] = '\0';printf("%s\n",szBuffer);if(strncmp(szBuffer,"226 Close",strlen("226 Close"))==0){break;}if(strncmp(szBuffer,"500 Syntax error",strlen("500 Syntax error"))==0) {break;}}return 0;}int cdfun(SOCKET sClient,char pathname[40]){int ret;szMessage[0]='\0';strcat(szMessage, "cd$");strcat(szMessage,pathname);ret = send(sClient, szMessage, strlen(szMessage)+1, 0);if (ret == 0)return 1;else if (ret == SOCKET_ERROR){printf("send() failed: %d\n", WSAGetLastError());return 1;}printf("Send %d bytes\n", ret);return 0;}int mdfun(SOCKET sClient,char pathname[20]){int ret;char szBuffer[160];//char *MSG="md$";szMessage[0]='\0';strcat(szMessage, "md$");//strcat(szMessage, "\\");strcat(szMessage,pathname);//strcpy(szMessage, MSG);ret = send(sClient, szMessage, strlen(szMessage)+1, 0);if (ret == 0)return 1;else if (ret == SOCKET_ERROR){printf("send() failed: %d\n", WSAGetLastError());return 1;}printf("Send %d bytes\n", ret);while(!bSendOnly){//读取流并显示ret = recv(sClient, szBuffer, 80, 0);if (ret == 0) // Graceful closereturn 1;else if (ret == SOCKET_ERROR){printf("recv() failed: %d\n", WSAGetLastError());return 1;}szBuffer[ret] = '\0';printf("%s",szBuffer);if(strncmp(szBuffer,"226 Close",strlen("226 Close"))==0){break;}if(strncmp(szBuffer,"500 Syntax error",strlen("500 Syntax error"))==0){break;}}return 0;}int delfun(SOCKET sClient,char name[20]){int ret;char szBuffer[80];szMessage[0]='\0';strcat(szMessage, "del$");strcat(szMessage,name);ret = send(sClient, szMessage, strlen(szMessage)+1, 0);if (ret == 0)return 1;else if (ret == SOCKET_ERROR){printf("send() failed: %d\n", WSAGetLastError());return 1;}printf("Send %d bytes\n", ret);while(!bSendOnly){ret = recv(sClient, szBuffer, 80, 0);if (ret == 0) // Graceful closereturn 1;else if (ret == SOCKET_ERROR){printf("recv() failed: %d\n", WSAGetLastError());return 1;}szBuffer[ret] = '\0';if(strncmp(szBuffer,"del ok",strlen("del ok"))==0){printf("del %s ok\n",name);break;}printf("%s",szBuffer);if(strncmp(szBuffer,"500 Syntax error",strlen("500 Syntax error"))==0) {break;}}return 0;}int usafun(){puts("------------------------------------------");puts("get：取远方的一个文件");puts("put：传给远方一个文件");puts("pwd：显示远主当前目录");puts("dir：列出远方当前目录");puts("md ：在远方新建文件夹");puts("cd ：改变远方当前目录");puts("？：显示你提供的命令");puts("quit ：退出返回");return 0;}//int quit()/****************server.c****************/#include <stdio.h>#include <winsock.h>#include <stdlib.h>#pragma comment(lib,"ws2_32.lib")WSADATA wsd;char sbuffer[80],rbuffer[80];//send and receive buffersint n,bytes;//countersSOCKET newsocket,ns_data;struct sockaddr_in remoteaddr; //remoteaddr_data;int port_connect=0;//port connect flagchar path[80]="";char order[100]="";//SOCKET s_data_port;int sy_error=1; // use for indicate Syntax error//server functionsint sdirfun(SOCKET newsocket);int sgetfun(SOCKET newsocket);int sputfun(SOCKET newsocket);int spwdfun(SOCKET newsocket);int scdfun(SOCKET newsocket);int smdfun(SOCKET newsocket);int sdelfun(SOCKET newsocket);void HandleError(char *func);//server functions end//MAINint main(int argc, char *argv[]){struct sockaddr_in localaddr;//local address structureSOCKET s;//s_data;//welcome socket and welcome socket for data connection,and port connection for connect to clientint addr_inlen;//address lenght variableif (WSAStartup(MAKEWORD(2,2), &wsd) != 0){WSACleanup();printf("WSAStartup failed\n");}memset(&localaddr,0,sizeof(localaddr));//clear localaddrs = socket(PF_INET, SOCK_STREAM, 0);if (s <0){printf("socket failed\n");}localaddr.sin_family = AF_INET;if(argc == 2)localaddr.sin_port = htons((u_short)atoi(argv[1]));elselocaladdr.sin_port = htons(2302);localaddr.sin_addr.s_addr = INADDR_ANY;if (bind(s,(struct sockaddr *)(&localaddr),sizeof(localaddr)) < 0){printf("Bind failed!\n");}//INFINITE LOOPwhile (1){ // while loop 1//LISTENlisten(s,3);addr_inlen = sizeof(remoteaddr);//ACCEPT main connection (control connection)newsocket = accept(s,(struct sockaddr *)(&remoteaddr),&addr_inlen);if (newsocket == INVALID_SOCKET) break;printf("connected to %s at port %d \n",inet_ntoa(remoteaddr.sin_addr),ntohs(localaddr.sin_port));//Respond with welcome message, FTP client requires thosesprintf(sbuffer,"200 Welcome \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);sprintf(sbuffer,"530 Log in \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);//INFINITE LOOPwhile (1) // while loop 2{n = 0;sy_error=1;while (1) // while loop 3{//RECEIVEbytes = recv(newsocket, &rbuffer[n], 1, 0);printf("rbuffer[%d]=%c\n",n,rbuffer[n]);if ((bytes < 0) || (bytes == 0))break;if (rbuffer[n] == '$'){rbuffer[n] = '\0';break;}if (rbuffer[n] != '\r')n++;} // end of while loop 3if ((bytes < 0) || (bytes == 0))break;printf("#The Server receives:# '%s' from client \n", rbuffer); //THE FTP COMMANDS HERE//LISTif(strncmp(rbuffer,"dir",3)==0){sdirfun(newsocket);}//当前目录if(strncmp(rbuffer,"pwd",3)==0){spwdfun(newsocket);}//改变目录if (strncmp(rbuffer,"cd",2)==0){scdfun(newsocket);}//GETif (strncmp(rbuffer,"get",3)==0){sgetfun(newsocket);}//PUTif (strncmp(rbuffer,"put",3)==0){sputfun(newsocket);}//MDif (strncmp(rbuffer,"md",2)==0){smdfun(newsocket);}if (strncmp(rbuffer,"del",3)==0){sdelfun(newsocket);}//QUITif (strncmp(rbuffer,"quit",4)==0){printf("quit \n");sprintf(sbuffer, "221 Bye bye ... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);sy_error=0;break;}//Syntax errorif (sy_error==1){printf("command unrecognized, non-implemented!\n");sprintf(sbuffer, "500 Syntax error. \n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);}} // end of while loop 2//CLOSE CONTROL SOCKETclosesocket(newsocket);printf("disconnected from %s at port %d, close control socket.\n",inet_ntoa(remoteaddr.sin_addr),ntohs(localaddr.sin_port));} // end of while loop 1//CLOSE WELCOME SOCKETclosesocket(s);printf("Welcome sockets close");return 0;}int sdirfun(SOCKET newsocket){char temp_buffer[80];printf("Equivalent to dir \n");order[0]='\0';strcat(order,"dir ");strcat(order,path);strcat(order," >tmp.txt");system(order);FILE *fin;fin=fopen("tmp.txt","r");sprintf(sbuffer, "125 Transfering... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);while (fgets(temp_buffer,80,fin)!=NULL){sprintf(sbuffer,"%s",temp_buffer); //if (port_connect==0)send(newsocket, sbuffer, strlen(sbuffer), 0);}fclose(fin);sprintf(sbuffer, "226 Transfer completed... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);system("del tmp.txt");//CLOSE the ns_data SOCKET or data port SOCKETif(port_connect==0){closesocket(ns_data);sprintf(sbuffer,"226 Close the data socket... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);ns_data = socket(AF_INET, SOCK_STREAM, 0);}sy_error=0;return 0;}int sgetfun(SOCKET newsocket){printf("RETR mode.\r\n");int i=4,k=0;char filename[20],temp_buffer[80];// identify the filename from rbuffer after the word "RETR "while (1) // while loop 4{//RECEIVEbytes = recv(newsocket, &rbuffer[i], 1, 0);printf("rbuffer[i]=%c\n",rbuffer[i]);if ((bytes < 0) || (bytes == 0))break;filename[k]=rbuffer[i];if (rbuffer[i] == '\0'){ /*end on LF*/filename[k] = '\0';break;}if (rbuffer[i] != '\r'){i++;k++;/*ignore CR's*/}} // end of while loop 4order[0]='\0';strcat(order,path);if(strlen(path)>0)strcat(order,"\\");strcat(order,filename);char *p_filename=order;FILE *fp;if( (fp=fopen(p_filename,"r")) == NULL ){sprintf(sbuffer, "Sorry, cannot open %s. Please try again.\r\n",filename);bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);sprintf(sbuffer, "226 Transfer completed... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);return 1;}else{printf("The file %s found,ready to transfer.\n",filename);sprintf(sbuffer, "125 Transfering... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);while (fgets(temp_buffer,80,fp)!=NULL){sprintf(sbuffer,"%s",temp_buffer); //if (port_connect==0)send(newsocket, sbuffer, strlen(sbuffer), 0);}//end of whilefclose(fp);sprintf(sbuffer, "226 Transfer completed... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);}sy_error=0;return 0;}int sputfun(SOCKET newsocket){printf("Equivalent to put. \n");int i=4,k=0;char filename[20];// identify the filename from rbuffer after the word "RETR "while (1){bytes = recv(newsocket, &rbuffer[i], 1, 0);if ((bytes < 0) || (bytes == 0))break;filename[k]=rbuffer[i];if (rbuffer[i] == '\0'){ /*end on LF*/filename[k] = '\0';break;}if (rbuffer[i] != '\r'){i++;k++;/*ignore CR's*/}} // end of whileorder[0]='\0';strcat(order,path);if(strlen(path)>0)strcat(order,"\\");strcat(order,filename);printf("filename=%s,",order);char *p_filename=order;FILE *fpse;if( (fpse=fopen(order,"w")) == NULL ){printf("open errer");return 1;}else{printf("The file %s found,ready to transfer.\n",filename);while(1){//读取流并显示int ret;ret = recv(newsocket, rbuffer, 80, 0);if (ret == 0) // Graceful closereturn 0;else if (ret == SOCKET_ERROR){printf("recv() failed: %d\n", WSAGetLastError());return 0;}if(strncmp(rbuffer,"226 Transfer",strlen("226 Transfer"))==0){break;}fprintf(fpse,"%s",rbuffer);}printf("RBUFFER=%s",rbuffer);fclose(fpse);}sy_error=0;return 0;}int spwdfun(SOCKET newsocket){printf("Equivalent to pwd \n");//order[0]='\0';//strcat(order,"dir ");//strcat(order,path);//strcat(order,);system("cd >tmp.txt");FILE *fin;fin=fopen("tmp.txt","r+");sprintf(sbuffer, "125 Transfering... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);char temp_buffer[160];while (fgets(temp_buffer,80,fin)!=NULL){temp_buffer[strlen(temp_buffer)-1]='\0';printf("temp_buffer=%s",temp_buffer);///////////////////////////////目录判定if(path[0]!='\0')sprintf(sbuffer,"%s\\%s",temp_buffer,path);elsesprintf(sbuffer,"%s",temp_buffer);///////////////////////////////if (port_connect==0)//send(ns_data, sbuffer, strlen(sbuffer), 0);send(newsocket, sbuffer, strlen(sbuffer), 0);}fclose(fin);sprintf(sbuffer, "226 Transfer completed... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);system("del tmp.txt");//CLOSE the ns_data SOCKET or data port SOCKETif(port_connect==0){closesocket(ns_data);sprintf(sbuffer,"226 Close the data socket... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);ns_data = socket(AF_INET, SOCK_STREAM, 0);}sy_error=0;return 0;}int scdfun(SOCKET newsocket){int i=3,k=0;char name[20],name2[20];int j,count=0;//path overfollowint pathlen;printf("Equivalent to cd \n");while (1){//RECEIVEbytes = recv(newsocket, &rbuffer[i], 1, 0);printf("rbuffer[i]=%c\n",rbuffer[i]);printf("bytes=%d\n",bytes);if ((bytes < 0) || (bytes == 0))break;name[k]=rbuffer[i];name2[k]=rbuffer[i];if (rbuffer[i] == '\0'){name[k] = '\0';name2[k] = '\0';break;}if (rbuffer[i] != '\r'){i++;k++;}}//end whileif(path[0]!='\0')strcat(path,"\\");strcat(path,name);if(strncmp(name2,"..",2)==0){pathlen=strlen(path);for(j=pathlen-1;j>=0;j--){if(path[j]=='\\'){path[j]='\0';count++;}if(count==2){//path[j]='\0';break;}}printf("%d=\n",j);path[j+1]='\0';}printf("path=%s",path);sy_error=0;return 0;}int smdfun(SOCKET newsocket){char name[20];int i=3,k=0;printf("Equivalent to md \n");while (1) // while loop 3{//RECEIVEbytes = recv(newsocket, &rbuffer[i], 1, 0);printf("rbuffer[i]=%c\n",rbuffer[i]);printf("bytes=%d\n",bytes);if ((bytes < 0) || (bytes == 0))break;name[k]=rbuffer[i];if (rbuffer[i] == '\0'){ /*end on LF*/name[k] = '\0';break;}if (rbuffer[i] != '\r'){i++;k++;/*ignore CR's*/}}order[0]='\0';strcat(order,"md ");strcat(order,path);if(strlen(path)>0)strcat(order,"\\");strcat(order,name);system(order);//CLOSE the ns_data SOCKET or data port SOCKETif(port_connect==0){//closesocket(ns_data);sprintf(sbuffer,"226 Close the data socket... \r\n");bytes = send(newsocket, sbuffer, strlen(sbuffer), 0);//ns_data = socket(AF_INET, SOCK_STREAM, 0);}sy_error=0;return 0;}int sdelfun(SOCKET newsocket){int i=3,k=0;char name[20];printf("Equivalent to del \n");while (1){//RECEIVEbytes = recv(newsocket, &rbuffer[i], 1, 0);printf("rbuffer[i]=%c\n",rbuffer[i]);printf("bytes=%d\n",bytes);if ((bytes < 0) || (bytes == 0))break;name[k]=rbuffer[i];if (rbuffer[i] == '\0'){name[k] = '\0';break;}if (rbuffer[i] != '\r'){i++;k++;}}//end whileorder[0]='\0';strcat(order,"rd ");strcat(order,path);if(path[0]!='\0')strcat(path,"\\");strcat(order,name);system(order);。