linux网络编程课程设计报告书.doc

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《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 <filename>
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。

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