问题描述
我正在尝试使用winsock2和UDP套接字编写文件传输程序。该文件以块形式传输，我正在尝试实现Go Back N算法以进行故障处理。这是我的服务器代码：
#include<iostream>
#include<fstream>
#include<cstring>
#include<winsock2.h>
#define PORT 8080
#define MAXLEN 1024
#define BLOCKSIZE 15
#define SEQNUMSIZE 2
#define DATALENSIZE 2
bool WritetoFile(char block[],std::ofstream& file,int n,int &expSeqNum,char seqnumchr[])
{
int i=0;
//char seqnumchr[SEQNUMSIZE+1];
strncpy(seqnumchr,block,SEQNUMSIZE);
seqnumchr[SEQNUMSIZE] = '\0';
int seqnum = std::stoi(seqnumchr);
if(seqnum != expSeqNum)
{
expSeqNum = seqnum;
return seqnum==-1?true:false;
}
printf("Sequence Number: %d exp %d\n",seqnum,expSeqNum);
char datalenchr[DATALENSIZE+1];
strncpy(datalenchr,block+SEQNUMSIZE,DATALENSIZE);
datalenchr[DATALENSIZE] = '\0';
int datalen = std::stoi(datalenchr);
char data[datalen+1];
strncpy(data,block+SEQNUMSIZE+DATALENSIZE,datalen);
data[datalen] = '\0';
file.write(data,datalen);
return false;
}
int main()
{
WSADATA wsaData;
SOCKET serverSocket;
SOCKADDR_IN serverAddr;
char buffer[MAXLEN];
SOCKADDR_IN clientAddr;
int clientAddrSize = sizeof(clientAddr);
int bytesReceived;
std::ofstream file("server.txt");
if( WSAStartup(MAKEWORD(2,2),&wsaData) != 0)
{
printf("Server: WSAStartup Failed with error %ld\n",WSAGetLastError());
WSACleanup();
return -1;
}
else
{
printf("Server: The Winsock DLL status is %s.\n",wsaData.szSystemStatus);
}
serverSocket = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
if(serverSocket == INVALID_SOCKET)
{
printf("Server: Error at socket(): %ld\n",WSAGetLastError());
WSACleanup();
return -1;
}
else { printf("Server: socket() is OK!\n"); }
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(PORT);
serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(serverSocket,(SOCKADDR *)&serverAddr,sizeof(serverAddr)) == SOCKET_ERROR)
{
printf("Server: bind() Failed! Error: %ld.\n",WSAGetLastError());
closesocket(serverSocket);
WSACleanup();
return -1;
}
else { printf("Server: bind() is OK!\n"); }
getsockname(serverSocket,(int *)sizeof(serverAddr));
printf("Server: Receiving IP(s) used: %s\n",inet_ntoa(serverAddr.sin_addr));
printf("Server: Receiving port used: %d\n",htons(serverAddr.sin_port));
bytesReceived = recvfrom(serverSocket,buffer,MAXLEN,(SOCKADDR *)&clientAddr,&clientAddrSize);
if(bytesReceived <= 0)
{
printf("Server: Connection closed with error code: %ld\n",WSAGetLastError());
}
else
{
buffer[bytesReceived] = '\0';
if(strcmp(buffer,"upload")==0)
{
printf("File upload started...\n");
sendto(serverSocket,"start",5,clientAddrSize);
int expSeqNum = 0;
while(true)
{
bytesReceived = recvfrom(serverSocket,&clientAddrSize);
if(bytesReceived <= 0)
{
printf("Server: Connection closed with error code: %ld\n",WSAGetLastError());
}
else
{
int tempExpNum = expSeqNum;
char seqnumchr[SEQNUMSIZE+1];
if(WritetoFile(buffer,file,bytesReceived,expSeqNum,seqnumchr))
{
printf("File upload finished!\n");
break;
}
if(expSeqNum != -1 && expSeqNum <= tempExpNum)
{
printf("Ack sent %d\n",expSeqNum);
if(expSeqNum == tempExpNum) expSeqNum++;
else expSeqNum = tempExpNum;
u_long mode = 1;
ioctlsocket(serverSocket,FIONBIO,&mode);
sendto(serverSocket,seqnumchr,SEQNUMSIZE,clientAddrSize);
mode = 0;
ioctlsocket(serverSocket,&mode);
}
}
}
}
}
getpeername(serverSocket,&clientAddrSize);
printf("Server: Sending IP used: %s\n",inet_ntoa(clientAddr.sin_addr));
printf("Server: Sending port used: %d\n",htons(clientAddr.sin_port));
if (closesocket(serverSocket) != 0)
printf("Server: closesocket() Failed! Error code: %ld\n",WSAGetLastError());
else
printf("Server: closesocket() is OK\n");
printf("Server: Cleaning up...\n");
if(WSACleanup() != 0)
printf("Server: WSACleanup() Failed! Error code: %ld\n",WSAGetLastError());
else
printf("Server: WSACleanup() is OK\n");
file.close();
return 0;
}
这是我的客户代码：
#include<iostream>
#include<fstream>
#include<vector>
#include<utility>
#include<map>
#include<iterator>
#include<cstring>
#include<string>
#include<winsock2.h>
#define PORT 8080
#define MAXLEN 1024
#define BLOCKSIZE 15
#define SEQNUMSIZE 2
#define DATALENSIZE 2
#define WINDOWSIZE 3
#define BLOCKTIMEOUT 10
bool ReadBlockFromFile(char str[],std::ifstream& file,int seqNum)
{
std::string seqN = std::to_string(seqNum);
seqN = std::string(SEQNUMSIZE - seqN.length(),'0') + seqN;
strcpy(str,seqN.c_str());
int datalen = BLOCKSIZE - SEQNUMSIZE - DATALENSIZE;
char data[datalen];
file.read(data,datalen);
bool eof = false;
if(file.eof())
{
eof = true;
if(file.gcount() != datalen)
{
std::string app(datalen - file.gcount(),'0');
strcat(data,app.c_str());
datalen = file.gcount();
}
}
std::string dataL = std::to_string(datalen);
dataL = std::string(DATALENSIZE - dataL.length(),'0') + dataL;
strcat(str,dataL.c_str());
strcat(str,data);
std::cout<<seqNum<<std::endl;
return eof?true:false;
}
void CheckAck(SOCKET& clientSocket,SOCKADDR_IN& serverAddr,std::map<int,std::pair<int,std::string>>& nonAckTimeData)
{
//printf("CheckAck\n");
u_long mode = 1;
ioctlsocket(clientSocket,&mode);
char buffer[MAXLEN];
int serverAddrSize = sizeof(serverAddr);
while (true)
{
int n = recvfrom(clientSocket,&serverAddrSize);
if(n ==-1)
{
int err = WSAGetLastError();
if(err != WSAEWOULDBLOCK)
{
printf("Client: recvfrom() Failed with error code %d\n",err);
}
break;
}
buffer[n] = '\0';
char seqN[SEQNUMSIZE+1];
strncpy(seqN,SEQNUMSIZE);
seqN[SEQNUMSIZE] = '\0';
int seqNum = std::stoi(seqN);
printf("Sequence number %d ackNowledgement received\n",seqNum);
nonAckTimeData.erase(seqNum);
}
mode = 0;
ioctlsocket(clientSocket,&mode);
for(std::map<int,std::string>>::iterator it = nonAckTimeData.begin(); it != nonAckTimeData.end(); it++)
{
it->second .first++;
if(it->second.first > BLOCKTIMEOUT)
{
printf("Sequence number %d timeouted!\n",it->first);
for(std::map<int,std::string>>::iterator it1 = it; it1 != nonAckTimeData.end(); it1++)
{
sendto(clientSocket,it1->second.second.c_str(),it1->second.second.size(),serverAddrSize);
it1->second.first = 0;
}
break;
}
}
}
int main()
{
WSADATA wsaData;
SOCKET clientSocket;
SOCKADDR_IN serverAddr,srcInfo;
char buffer[MAXLEN];
int serverAddrSize = sizeof(serverAddr);
std::ifstream file("client.txt");
std::map<int,std::string>> nonAckTimeData;
bool endFile = false;
if( WSAStartup(MAKEWORD(2,&wsaData) != 0)
{
printf("Client: WSAStartup Failed with error %ld\n",WSAGetLastError());
WSACleanup();
return -1;
}
else
{
printf("Client: The Winsock DLL status is %s.\n",wsaData.szSystemStatus);
}
clientSocket = socket(AF_INET,IPPROTO_UDP);
if(clientSocket == INVALID_SOCKET)
{
printf("Client: Error at socket(): %ld\n",WSAGetLastError());
WSACleanup();
return -1;
}
else { printf("Client: socket() is OK!\n"); }
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(PORT);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
sendto(clientSocket,"upload",6,serverAddrSize);
int n = recvfrom(clientSocket,&serverAddrSize);
if(n <= 0)
{
printf("Client: Connection closed with error code: %ld\n",WSAGetLastError());
}
else
{
buffer[n] = '\0';
if(strcmp(buffer,"start")==0)
{
printf("File upload started...\n");
int seqNum = 0;
while(true)
{
int ackLen = nonAckTimeData.size();
if(ackLen < WINDOWSIZE)
{
if(!endFile)
{
bool endF = ReadBlockFromFile(buffer,seqNum);
sendto(clientSocket,BLOCKSIZE,serverAddrSize);
nonAckTimeData[seqNum] = std::make_pair(0,buffer);
if(endF)
{
endFile = endF;
}
seqNum ++;
}
else if(ackLen == 0)
{
std::string endFileAck = "-1" + std::string(BLOCKSIZE - 2,'0');
sendto(clientSocket,endFileAck.c_str(),serverAddrSize);
break;
}
}
CheckAck(clientSocket,serverAddr,nonAckTimeData);
}
}
}
memset(&srcInfo,sizeof(srcInfo));
int len = sizeof(srcInfo);
getsockname(clientSocket,(SOCKADDR *)&srcInfo,&len);
printf("Client: Sending IP(s) used: %s\n",inet_ntoa(srcInfo.sin_addr));
printf("Client: Sending port used: %d\n",htons(srcInfo.sin_port));
getpeername(clientSocket,(int *)sizeof(serverAddr));
printf("Client: Receiving IP used: %s\n",inet_ntoa(serverAddr.sin_addr));
printf("Client: Receiving port used: %d\n",htons(serverAddr.sin_port));
printf("Client: Finished sending. Closing the sending socket...\n");
if (closesocket(clientSocket) != 0)
printf("Client: closesocket() Failed! Error code: %ld\n",WSAGetLastError());
else
printf("Server: closesocket() is OK\n");
printf("Client: Cleaning up...\n");
if(WSACleanup() != 0)
printf("Client: WSACleanup() Failed! Error code: %ld\n",WSAGetLastError());
else
printf("Client: WSACleanup() is OK\n");
file.close();
return 0;
}
这是服务器输出：
Server: The Winsock DLL status is Running.
Server: socket() is OK!
Server: bind() is OK!
Server: Receiving IP(s) used: 0.0.0.0
Server: Receiving port used: 8080
File upload started...
Sequence Number: 0 exp 0
Ack sent 0
Sequence Number: 1 exp 1
Ack sent 1
Sequence Number: 2 exp 2
Ack sent 2
Ack sent 0
Ack sent 1
Ack sent 2
Sequence Number: 3 exp 3
Ack sent 3
Sequence Number: 4 exp 4
Ack sent 4
Sequence Number: 5 exp 5
Ack sent 5
Ack sent 3
Ack sent 4
Ack sent 5
Sequence Number: 6 exp 6
Ack sent 6
Sequence Number: 7 exp 7
Ack sent 7
Sequence Number: 8 exp 8
Ack sent 8
Ack sent 6
Ack sent 7
Ack sent 8
Ack sent 6
Ack sent 7
Ack sent 8
Sequence Number: 9 exp 9
Ack sent 9
Sequence Number: 10 exp 10
Ack sent 10
Sequence Number: 11 exp 11
Ack sent 11
Ack sent 9
Ack sent 10
Ack sent 11
Ack sent 9
Ack sent 10
Ack sent 11
Sequence Number: 12 exp 12
Ack sent 12
Ack sent 10
Ack sent 11
Ack sent 12
Sequence Number: 13 exp 13
Ack sent 13
Sequence Number: 14 exp 14
Ack sent 14
Ack sent 13
Ack sent 14
Ack sent 13
Ack sent 14
File upload finished!
Server: Sending IP used: 127.0.0.1
Server: Sending port used: 62073
Server: closesocket() is OK
Server: Cleaning up...
Server: WSACleanup() is OK
这是我的客户输出
Client: The Winsock DLL status is Running.
Client: socket() is OK!
File upload started...
0
1
2
Sequence number 0 timeouted!
Sequence number 0 ackNowledgement received
Sequence number 1 ackNowledgement received
Sequence number 2 ackNowledgement received
Sequence number 0 ackNowledgement received
Sequence number 1 ackNowledgement received
Sequence number 2 ackNowledgement received
3
4
5
Sequence number 3 timeouted!
Sequence number 3 ackNowledgement received
Sequence number 4 ackNowledgement received
Sequence number 5 ackNowledgement received
Sequence number 3 ackNowledgement received
Sequence number 4 ackNowledgement received
Sequence number 5 ackNowledgement received
6
7
8
Sequence number 6 timeouted!
Sequence number 6 timeouted!
Sequence number 6 ackNowledgement received
Sequence number 7 ackNowledgement received
Sequence number 8 ackNowledgement received
Sequence number 6 ackNowledgement received
Sequence number 7 ackNowledgement received
Sequence number 8 ackNowledgement received
Sequence number 6 ackNowledgement received
Sequence number 7 ackNowledgement received
Sequence number 8 ackNowledgement received
9
10
11
Sequence number 9 timeouted!
Sequence number 9 timeouted!
Sequence number 9 ackNowledgement received
12
Sequence number 10 timeouted!
Sequence number 10 ackNowledgement received
Sequence number 11 ackNowledgement received
Sequence number 9 ackNowledgement received
Sequence number 10 ackNowledgement received
Sequence number 11 ackNowledgement received
Sequence number 9 ackNowledgement received
Sequence number 10 ackNowledgement received
Sequence number 11 ackNowledgement received
Sequence number 12 ackNowledgement received
Sequence number 10 ackNowledgement received
Sequence number 11 ackNowledgement received
Sequence number 12 ackNowledgement received
13
14
Sequence number 13 timeouted!
Sequence number 13 timeouted!
Sequence number 13 ackNowledgement received
Sequence number 14 ackNowledgement received
Sequence number 13 ackNowledgement received
Sequence number 14 ackNowledgement received
Sequence number 13 ackNowledgement received
Sequence number 14 ackNowledgement received
Client: Sending IP(s) used: 0.0.0.0
Client: Sending port used: 62073
Client: Receiving IP used: 127.0.0.1
Client: Receiving port used: 8080
Client: Finished sending. Closing the sending socket...
Server: closesocket() is OK
Client: Cleaning up...
Client: WSACleanup() is OK
客户端部分读取文件，并一次将定义大小的块发送到服务器。客户端窗口大小当前为3，因此在继续操作之前，它会等待确认窗口中的所有3个块。服务器收到一个阻止并立即发送确认。 为什么即使服务器立即发送确认，块仍会超时？此外，客户端仅在发送3个块后才收到确认消息，为什么会这样呢？我在做什么错了？
解决方法
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