TFTP 服务器 - 线程版本问题
TFTP Server - Issue With Threaded Version
我创建了一个简单的 tftp 服务器,它只处理读取请求 (RRQ)。在我开始制作服务器的多线程版本之前,一切都运行良好。在应用程序中,我只是在主线程中接收请求,然后将请求转发到执行数据包分析的新线程。因此,我需要将套接字、接收到的数据包和包含客户端信息的 sockaddr_in 结构转发给线程。话虽如此,我创建了一个结构来保存所有这些并将它们转发给 pthread。
我怀疑问题出在struct clientThread
初始化部分和转发部分;因为我确定 connection_handler
.
内部处理的正确性
注意:可以使用linux自带的tftp客户端进行测试
这是我目前编写的代码(线程版)。请使用 -pthread
标志编译它...
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <pthread.h>
#include <time.h>
#define TIMEOUT 5000
#define RETRIES 3
void *connection_handler(void *);
struct clientThread
{
int clientSock;
char buffer[1024];
struct sockaddr_in client;
};
int main()
{
char buffer[1024];
int udpSocket, client_socket, nBytes;
struct sockaddr_in serverAddr, client;
socklen_t addr_size;
udpSocket = socket(AF_INET, SOCK_DGRAM, 0);
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(69);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serverAddr.sin_zero, '[=10=]', sizeof serverAddr.sin_zero);
bind(udpSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr));
while(1)
{
memset(buffer, 0, 1024);
nBytes = recvfrom(udpSocket,buffer,1024,0,(struct sockaddr *)&client, &addr_size);
// Creating a thread and passing the packet received, the socket and the sockaddr_in struct...
pthread_t client_thread;
struct clientThread clientT;
strcpy(clientT.buffer,buffer);
clientT.clientSock = udpSocket;
clientT.client = client;
pthread_create(&client_thread, NULL, connection_handler, &clientT);
}
return 0;
}
void* connection_handler (void *clientThreaded)
{
char buffer[1024], filename[200], mode[20], *bufindex, opcode;
struct clientThread *cthread = clientThreaded;
int udpSocket = cthread->clientSock;
strcpy(buffer, cthread->buffer);
struct sockaddr_in client = cthread->client;
bufindex = buffer;
bufindex++;
// Extracting the opcode from the packet...
opcode = *bufindex++;
// Extracting the filename from the packet...
strncpy(filename, bufindex, sizeof(filename)-1);
bufindex += strlen(filename) + 1;
// Extracting the mode from the packet...
strncpy(mode, bufindex, sizeof(mode)-1);
// If we received an RRQ...
if (opcode == 1)
{
puts("Received RRQ Request");
struct timeval tv;
tv.tv_sec = 5;
char path[70] = "tmp/";
char filebuf [1024];
int count = 0, i; // Number of data portions sent
unsigned char packetbuf[1024];
char recvbuf[1024];
socklen_t recv_size;
socklen_t optionslength = sizeof(tv);
setsockopt(udpSocket, SOL_SOCKET, SO_RCVTIMEO, &tv, optionslength);
FILE *fp;
char fullpath[200];
strcpy(fullpath, path);
strncat(fullpath, filename, sizeof(fullpath) -1);
fp = fopen(fullpath, "r");
if (fp == NULL)
perror("");
memset(filebuf, 0, sizeof(filebuf));
while (1)
{
int acked = 0;
int ssize = fread(filebuf, 1 , 512, fp);
count++;
sprintf((char *) packetbuf, "%c%c%c%c", 0x00, 0x03, 0x00, 0x00);
memcpy((char *) packetbuf + 4, filebuf, ssize);
packetbuf[2] = (count & 0xFF00) >> 8;
packetbuf[3] = (count & 0x00FF);
int len = 4 + ssize;
memset(recvbuf, 0, 1024);
printf("\nSending Packet #%i", count);
sendto(udpSocket, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client));
for (i=0; i<RETRIES; i++)
{
int result = recvfrom(udpSocket, recvbuf, 1024, 0, (struct sockaddr *) &client, &recv_size);
if ((result == -1) && ((errno == EAGAIN) || (errno == EWOULDBLOCK)))
{
sendto(udpSocket, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client));
printf("\nRetransmitting Packet #%i", count);
}
else if (result == -1)
{
// Handle Error
}
else
{
acked++;
printf("\nReceived ACK For Data Packet #%i", count);
break;
}
}
if (acked!=1)
{
puts("\nGave Up Transmission After 3 Retries");
break;
}
if (ssize != 512)
break;
}
}
return 0;
}
这是我的非线程版本代码...
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#define TIMEOUT 5000
#define RETRIES 3
int main()
{
int udpSocket, nBytes;
char buffer[1024], filename[200], mode[20], *bufindex, opcode;
struct sockaddr_in serverAddr, client;
struct sockaddr_storage serverStorage;
socklen_t addr_size;
udpSocket = socket(AF_INET, SOCK_DGRAM, 0);
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(69);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serverAddr.sin_zero, '[=11=]', sizeof serverAddr.sin_zero);
bind(udpSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr));
while(1)
{
memset(buffer, 0, 1024);
nBytes = recvfrom(udpSocket,buffer,1024,0,(struct sockaddr *)&client, &addr_size);
printf("%s",buffer);
bufindex = buffer;
bufindex++;
// Extracting the opcode from the packet...
opcode = *bufindex++;
// Extracting the filename from the packet...
strncpy(filename, bufindex, sizeof(filename)-1);
bufindex += strlen(filename) + 1;
// Extracting the mode from the packet...
strncpy(mode, bufindex, sizeof(mode)-1);
// If we received an RRQ...
if (opcode == 1)
{
puts("Received RRQ Request");
struct timeval tv;
tv.tv_sec = 5;
char path[70] = "tmp/";
char filebuf [1024];
int count = 0, i; // Number of data portions sent
unsigned char packetbuf[1024];
char recvbuf[1024];
socklen_t recv_size;
socklen_t optionslength = sizeof(tv);
setsockopt(udpSocket, SOL_SOCKET, SO_RCVTIMEO, &tv, optionslength);
FILE *fp;
char fullpath[200];
strcpy(fullpath, path);
strncat(fullpath, filename, sizeof(fullpath) -1);
fp = fopen(fullpath, "r");
if (fp == NULL)
perror("");
memset(filebuf, 0, sizeof(filebuf));
while (1)
{
int acked = 0;
int ssize = fread(filebuf, 1 , 512, fp);
count++;
sprintf((char *) packetbuf, "%c%c%c%c", 0x00, 0x03, 0x00, 0x00);
memcpy((char *) packetbuf + 4, filebuf, ssize);
packetbuf[2] = (count & 0xFF00) >> 8;
packetbuf[3] = (count & 0x00FF);
int len = 4 + ssize;
memset(recvbuf, 0, 1024);
printf("\nSending Packet #%i", count);
sendto(udpSocket, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client));
for (i=0; i<RETRIES; i++)
{
int result = recvfrom(udpSocket, recvbuf, 1024, 0, (struct sockaddr *) &client, &recv_size);
if ((result == -1) && ((errno == EAGAIN) || (errno == EWOULDBLOCK)))
{
sendto(udpSocket, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client));
printf("\nRetransmitting Packet #%i", count);
}
else if (result == -1)
{
// Handle Error
}
else
{
acked++;
printf("\nReceived ACK For Data Packet #%i", count);
break;
}
}
if (acked!=1)
{
puts("\nGave Up Transmission After 3 Retries");
break;
}
if (ssize != 512)
break;
}
}
}
return 0;
}
提前致谢:)
这里您的连接处理程序是错误的,因为在您传递给每个线程的套接字上没有任何锁定。
大多数基于 udp 的服务器实际上并没有分叉多线程。 TCP 服务器可以做到这一点,因为每次接受你都会得到一个新的套接字,它可以被委托给一个不会被任何其他线程使用的新线程。
但对于 udp,您基本上对所有线程使用相同的套接字,这是不对的。如果您要在套接字上提供保护,您可以使其工作,但您将失去通过使其成为多线程而试图获得的好处。
您在端口 69 上循环侦听,但实际数据传输将从另一个随机选择的端口执行(请阅读 RFC 1350)。
然后你的主循环必须为每个新传输创建一个新线程,这个新线程应该接收一个结构,其中包含要服务的文件的路径、目的地IP/port、随机选择的本地端口等
将结构指针传递给线程时,您必须考虑的是支持该结构的内存。
在你的情况下
struct clientThread clientT;
是在堆栈中动态创建的,当然结构是 "discarded" 当代码块超出范围时(在你的情况下在每个循环中)这意味着你正在传递一个指向 "soon to be garbage" 到刚刚创建的线程。
我建议在将结构传递给刚刚创建的线程时使用 malloc/free。
最后,您的主线程(调度程序)应维护一个考虑所有已创建线程及其状态的结构。这对于检测死线程或在有传输正在进行时需要关闭主程序是必要的。
如您所见,即使是像 TFTP 这样的简单协议,实现服务器也不是一件容易的事。
我创建了一个简单的 tftp 服务器,它只处理读取请求 (RRQ)。在我开始制作服务器的多线程版本之前,一切都运行良好。在应用程序中,我只是在主线程中接收请求,然后将请求转发到执行数据包分析的新线程。因此,我需要将套接字、接收到的数据包和包含客户端信息的 sockaddr_in 结构转发给线程。话虽如此,我创建了一个结构来保存所有这些并将它们转发给 pthread。
我怀疑问题出在struct clientThread
初始化部分和转发部分;因为我确定 connection_handler
.
注意:可以使用linux自带的tftp客户端进行测试
这是我目前编写的代码(线程版)。请使用 -pthread
标志编译它...
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <pthread.h>
#include <time.h>
#define TIMEOUT 5000
#define RETRIES 3
void *connection_handler(void *);
struct clientThread
{
int clientSock;
char buffer[1024];
struct sockaddr_in client;
};
int main()
{
char buffer[1024];
int udpSocket, client_socket, nBytes;
struct sockaddr_in serverAddr, client;
socklen_t addr_size;
udpSocket = socket(AF_INET, SOCK_DGRAM, 0);
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(69);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serverAddr.sin_zero, '[=10=]', sizeof serverAddr.sin_zero);
bind(udpSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr));
while(1)
{
memset(buffer, 0, 1024);
nBytes = recvfrom(udpSocket,buffer,1024,0,(struct sockaddr *)&client, &addr_size);
// Creating a thread and passing the packet received, the socket and the sockaddr_in struct...
pthread_t client_thread;
struct clientThread clientT;
strcpy(clientT.buffer,buffer);
clientT.clientSock = udpSocket;
clientT.client = client;
pthread_create(&client_thread, NULL, connection_handler, &clientT);
}
return 0;
}
void* connection_handler (void *clientThreaded)
{
char buffer[1024], filename[200], mode[20], *bufindex, opcode;
struct clientThread *cthread = clientThreaded;
int udpSocket = cthread->clientSock;
strcpy(buffer, cthread->buffer);
struct sockaddr_in client = cthread->client;
bufindex = buffer;
bufindex++;
// Extracting the opcode from the packet...
opcode = *bufindex++;
// Extracting the filename from the packet...
strncpy(filename, bufindex, sizeof(filename)-1);
bufindex += strlen(filename) + 1;
// Extracting the mode from the packet...
strncpy(mode, bufindex, sizeof(mode)-1);
// If we received an RRQ...
if (opcode == 1)
{
puts("Received RRQ Request");
struct timeval tv;
tv.tv_sec = 5;
char path[70] = "tmp/";
char filebuf [1024];
int count = 0, i; // Number of data portions sent
unsigned char packetbuf[1024];
char recvbuf[1024];
socklen_t recv_size;
socklen_t optionslength = sizeof(tv);
setsockopt(udpSocket, SOL_SOCKET, SO_RCVTIMEO, &tv, optionslength);
FILE *fp;
char fullpath[200];
strcpy(fullpath, path);
strncat(fullpath, filename, sizeof(fullpath) -1);
fp = fopen(fullpath, "r");
if (fp == NULL)
perror("");
memset(filebuf, 0, sizeof(filebuf));
while (1)
{
int acked = 0;
int ssize = fread(filebuf, 1 , 512, fp);
count++;
sprintf((char *) packetbuf, "%c%c%c%c", 0x00, 0x03, 0x00, 0x00);
memcpy((char *) packetbuf + 4, filebuf, ssize);
packetbuf[2] = (count & 0xFF00) >> 8;
packetbuf[3] = (count & 0x00FF);
int len = 4 + ssize;
memset(recvbuf, 0, 1024);
printf("\nSending Packet #%i", count);
sendto(udpSocket, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client));
for (i=0; i<RETRIES; i++)
{
int result = recvfrom(udpSocket, recvbuf, 1024, 0, (struct sockaddr *) &client, &recv_size);
if ((result == -1) && ((errno == EAGAIN) || (errno == EWOULDBLOCK)))
{
sendto(udpSocket, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client));
printf("\nRetransmitting Packet #%i", count);
}
else if (result == -1)
{
// Handle Error
}
else
{
acked++;
printf("\nReceived ACK For Data Packet #%i", count);
break;
}
}
if (acked!=1)
{
puts("\nGave Up Transmission After 3 Retries");
break;
}
if (ssize != 512)
break;
}
}
return 0;
}
这是我的非线程版本代码...
#include <stdio.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <time.h>
#define TIMEOUT 5000
#define RETRIES 3
int main()
{
int udpSocket, nBytes;
char buffer[1024], filename[200], mode[20], *bufindex, opcode;
struct sockaddr_in serverAddr, client;
struct sockaddr_storage serverStorage;
socklen_t addr_size;
udpSocket = socket(AF_INET, SOCK_DGRAM, 0);
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(69);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serverAddr.sin_zero, '[=11=]', sizeof serverAddr.sin_zero);
bind(udpSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr));
while(1)
{
memset(buffer, 0, 1024);
nBytes = recvfrom(udpSocket,buffer,1024,0,(struct sockaddr *)&client, &addr_size);
printf("%s",buffer);
bufindex = buffer;
bufindex++;
// Extracting the opcode from the packet...
opcode = *bufindex++;
// Extracting the filename from the packet...
strncpy(filename, bufindex, sizeof(filename)-1);
bufindex += strlen(filename) + 1;
// Extracting the mode from the packet...
strncpy(mode, bufindex, sizeof(mode)-1);
// If we received an RRQ...
if (opcode == 1)
{
puts("Received RRQ Request");
struct timeval tv;
tv.tv_sec = 5;
char path[70] = "tmp/";
char filebuf [1024];
int count = 0, i; // Number of data portions sent
unsigned char packetbuf[1024];
char recvbuf[1024];
socklen_t recv_size;
socklen_t optionslength = sizeof(tv);
setsockopt(udpSocket, SOL_SOCKET, SO_RCVTIMEO, &tv, optionslength);
FILE *fp;
char fullpath[200];
strcpy(fullpath, path);
strncat(fullpath, filename, sizeof(fullpath) -1);
fp = fopen(fullpath, "r");
if (fp == NULL)
perror("");
memset(filebuf, 0, sizeof(filebuf));
while (1)
{
int acked = 0;
int ssize = fread(filebuf, 1 , 512, fp);
count++;
sprintf((char *) packetbuf, "%c%c%c%c", 0x00, 0x03, 0x00, 0x00);
memcpy((char *) packetbuf + 4, filebuf, ssize);
packetbuf[2] = (count & 0xFF00) >> 8;
packetbuf[3] = (count & 0x00FF);
int len = 4 + ssize;
memset(recvbuf, 0, 1024);
printf("\nSending Packet #%i", count);
sendto(udpSocket, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client));
for (i=0; i<RETRIES; i++)
{
int result = recvfrom(udpSocket, recvbuf, 1024, 0, (struct sockaddr *) &client, &recv_size);
if ((result == -1) && ((errno == EAGAIN) || (errno == EWOULDBLOCK)))
{
sendto(udpSocket, packetbuf, len, 0, (struct sockaddr *) &client, sizeof(client));
printf("\nRetransmitting Packet #%i", count);
}
else if (result == -1)
{
// Handle Error
}
else
{
acked++;
printf("\nReceived ACK For Data Packet #%i", count);
break;
}
}
if (acked!=1)
{
puts("\nGave Up Transmission After 3 Retries");
break;
}
if (ssize != 512)
break;
}
}
}
return 0;
}
提前致谢:)
这里您的连接处理程序是错误的,因为在您传递给每个线程的套接字上没有任何锁定。
大多数基于 udp 的服务器实际上并没有分叉多线程。 TCP 服务器可以做到这一点,因为每次接受你都会得到一个新的套接字,它可以被委托给一个不会被任何其他线程使用的新线程。
但对于 udp,您基本上对所有线程使用相同的套接字,这是不对的。如果您要在套接字上提供保护,您可以使其工作,但您将失去通过使其成为多线程而试图获得的好处。
您在端口 69 上循环侦听,但实际数据传输将从另一个随机选择的端口执行(请阅读 RFC 1350)。 然后你的主循环必须为每个新传输创建一个新线程,这个新线程应该接收一个结构,其中包含要服务的文件的路径、目的地IP/port、随机选择的本地端口等
将结构指针传递给线程时,您必须考虑的是支持该结构的内存。 在你的情况下
struct clientThread clientT;
是在堆栈中动态创建的,当然结构是 "discarded" 当代码块超出范围时(在你的情况下在每个循环中)这意味着你正在传递一个指向 "soon to be garbage" 到刚刚创建的线程。
我建议在将结构传递给刚刚创建的线程时使用 malloc/free。
最后,您的主线程(调度程序)应维护一个考虑所有已创建线程及其状态的结构。这对于检测死线程或在有传输正在进行时需要关闭主程序是必要的。
如您所见,即使是像 TFTP 这样的简单协议,实现服务器也不是一件容易的事。