《Linux网络编程》
课程设计
班级：
姓名：
指导老师：
一、设计背景
Linux操作系统作为一个开源的操作系统被越来越多的人所应用，它的好处在于操作系统源代码的公开化！只要是基于GNU公约的软件你都可以任意使用并修改它的源代码。通过这次课程设计能更好的学习网络编程知识和掌握LINUX平台上应用程序设计开发的过程，将大学四年所学知识综合运用，为未来的工作学习打下基础。
二、设计目的
1、学习epoll 跟FTP被动模式
2、掌握linux基本命令，例如ls、cd、login；
3、学会如何编译、运行
三、环境要求
1、centos 64位操作系统
2、gcc编译器
四、设计原理
4．1客户端
客户端程序的主要任务有以下3个：
（1）、分析用户输入的命令。
（2）、根据命令向服务器发出请求
（3）、接受服务器返回请求的结果
客户端为用户提供了3种命令：（1）、get:从服务器下载文件（2）、list:列出客户端当前目录的内容（3）、quit离开
4.2 服务器端
（1）、分析请求代码。
（2）、根据请求代码做相应的处理
（3）、等待返回结果或者应答信息
五、软件测试结果
六、部分主代码
#include "ftserve.h"
int main(int argc, char *argv[])
{
int sock_listen, sock_control, port, pid;
if (argc != 2) {
printf("usage: ./ftserve port\n");
exit(0);
}
port = atoi(argv[1]);
// create socket
if ((sock_listen = socket_create(port)) < 0 ) { perror("Error creating socket");
exit(1);
}
while(1) { // wait for client request
// create new socket for control connection
if ((sock_control = socket_accept(sock_listen)) < 0 )
break;
// create child process to do actual file transfer
if ((pid = fork()) < 0) {
perror("Error forking child process");
} else if (pid == 0) {
close(sock_listen);
ftserve_process(sock_control);
close(sock_control);
exit(0);
}
close(sock_control);
}
close(sock_listen);
return 0;
}
/**
* Send file specified in filename over data connection, sending * control message over control connection
* Handles case of null or invalid filename
*/
void ftserve_retr(int sock_control, int sock_data, char* filename) {
FILE* fd = NULL;
char data[MAXSIZE];
size_t num_read;
fd = fopen(filename, "r");
if (!fd) {
// send error code (550 Requested action not taken)
send_response(sock_control, 550);
} else {
// send okay (150 File status okay)
send_response(sock_control, 150);
do {
num_read = fread(data, 1, MAXSIZE, fd);
if (num_read < 0) {
printf("error in fread()\n");
}
// send block
if (send(sock_data, data, num_read, 0) < 0)
perror("error sending file\n");
} while (num_read > 0);
// send message: 226: closing conn, file transfer successful
send_response(sock_control, 226);
fclose(fd);
}
}
/**
* Send list of files in current directory
* over data connection
* Return -1 on error, 0 on success
*/
int ftserve_list(int sock_data, int sock_control)
{
char data[MAXSIZE];
size_t num_read;
FILE* fd;
int rs = system("ls -l | tail -n+2 > tmp.txt");
if ( rs < 0) {
exit(1);
}
fd = fopen("tmp.txt", "r");
if (!fd) {
exit(1);
}
/* Seek to the beginning of the file */
fseek(fd, SEEK_SET, 0);
send_response(sock_control, 1); //starting
memset(data, 0, MAXSIZE);
while ((num_read = fread(data, 1, MAXSIZE, fd)) > 0) { if (send(sock_data, data, num_read, 0) < 0) {
perror("err");
}
memset(data, 0, MAXSIZE);
}
fclose(fd);
send_response(sock_control, 226); // send 226
return 0;
}
/**
* Open data connection to client
* Returns: socket for data connection
* or -1 on error
*/
int ftserve_start_data_conn(int sock_control)
{
char buf[1024];
int wait, sock_data;
// Wait for go-ahead on control conn
if (recv(sock_control, &wait, sizeof wait, 0) < 0 ) { perror("Error while waiting");
return -1;
}
// Get client address
struct sockaddr_in client_addr;
socklen_t len = sizeof client_addr;
getpeername(sock_control, (struct sockaddr*)&client_addr, &len);
inet_ntop(AF_INET, &client_addr.sin_addr, buf, sizeof(buf));
// Initiate data connection with client
if ((sock_data = socket_connect(CLIENT_PORT_ID, buf)) < 0) return -1;
return sock_data;
}
/**
* Authenticate a user's credentials
* Return 1 if authenticated, 0 if not
*/
int ftserve_check_user(char*user, char*pass)
{
char username[MAXSIZE];
char password[MAXSIZE];
char *pch;
char buf[MAXSIZE];
char *line = NULL;
size_t num_read;
size_t len = 0;
FILE* fd;
int auth = 0;
fd = fopen(".auth", "r");
if (fd == NULL) {
perror("file not found");
exit(1);
}
while ((num_read = getline(&line, &len, fd)) != -1) {
memset(buf, 0, MAXSIZE);
strcpy(buf, line);
pch = strtok (buf," ");
strcpy(username, pch);
if (pch != NULL) {
pch = strtok (NULL, " ");
strcpy(password, pch);
}
// remove end of line and whitespace
trimstr(password, (int)strlen(password));
if ((strcmp(user,username)==0) && (strcmp(pass,password)==0)) { auth = 1;
break;
}
}
free(line);
fclose(fd);
return auth;
}
/**
* Log in connected client
*/
int ftserve_login(int sock_control)
{
char buf[MAXSIZE];
char user[MAXSIZE];
char pass[MAXSIZE];
memset(user, 0, MAXSIZE);
memset(pass, 0, MAXSIZE);
memset(buf, 0, MAXSIZE);
// Wait to recieve username
if ( (recv_data(sock_control, buf, sizeof(buf)) ) == -1) { perror("recv error\n");
exit(1);
}
int i = 5;
int n = 0;
while (buf[i] != 0)
user[n++] = buf[i++];
// tell client we're ready for password
send_response(sock_control, 331);
// Wait to recieve password
memset(buf, 0, MAXSIZE);
if ( (recv_data(sock_control, buf, sizeof(buf)) ) == -1) { perror("recv error\n");
exit(1);
}
i = 5;
n = 0;
while (buf[i] != 0) {
pass[n++] = buf[i++];
}
return (ftserve_check_user(user, pass));
}
/**
* Wait for command from client and
* send response
* Returns response code
*/
int ftserve_recv_cmd(int sock_control, char*cmd, char*arg)
{
int rc = 200;
char buffer[MAXSIZE];
memset(buffer, 0, MAXSIZE);
memset(cmd, 0, 5);
memset(arg, 0, MAXSIZE);
// Wait to recieve command
if ((recv_data(sock_control, buffer, sizeof(buffer)) ) == -1) { perror("recv error\n");
return -1;
}
strncpy(cmd, buffer, 4);
char *tmp = buffer + 5;
strcpy(arg, tmp);
if (strcmp(cmd, "QUIT")==0) {
rc = 221;
} else if((strcmp(cmd, "USER")==0) || (strcmp(cmd, "PASS")==0) || (strcmp(cmd, "LIST")==0) || (strcmp(cmd, "RETR")==0)) { rc = 200;
} else { //invalid command
rc = 502;
}
send_response(sock_control, rc);
return rc;
}
/**
* Child process handles connection to client
*/
void ftserve_process(int sock_control)
{
int sock_data;
char cmd[5];
char arg[MAXSIZE];
// Send welcome message
send_response(sock_control, 220);
// Authenticate user
if (ftserve_login(sock_control) == 1) {
send_response(sock_control, 230);
} else {
send_response(sock_control, 430);
exit(0);
}
while (1) {
// Wait for command
int rc = ftserve_recv_cmd(sock_control, cmd, arg);
if ((rc < 0) || (rc == 221)) {
break;
}
if (rc == 200 ) {
// Open data connection with client
if ((sock_data = ftserve_start_data_conn(sock_control)) < 0) {
close(sock_control);
exit(1);
}
// Execute command
if (strcmp(cmd, "LIST")==0) { // Do list
ftserve_list(sock_data, sock_control);
} else if (strcmp(cmd, "RETR")==0) { // Do get
ftserve_retr(sock_control, sock_data, arg);
}
// Close data connection
close(sock_data);
}
}
}
七、设计总结
通过本次的linux程序与设计课程设计让我们学会使用linux系统和socket，极大的丰富了linux系统下编程和网络方面的知识，锻炼了动手能力，为以后的工作学习打下了坚实的基础。