c++ client socket simultaneously connection - c++

hello i have a client socket application, that connect at the same time, with more than 5000 server with tcpip in linux, but when i open the socket connection, almost all connections, retrieve the error Operation now in progress.
Here my client socket connect code:
how can i doing a good thousands simultaneously socket conecction at the same time???
sorry for my english.
here my code :
struct sockaddr_in echoserver;
struct sockaddr_in sa_loc;
char aport[64];
int optval = 1;
int sock;
memset(&echoserver, 0, sizeof (echoserver));
echoserver.sin_family = AF_INET;
echoserver.sin_addr.s_addr = inet_addr(server.c_str());
echoserver.sin_port = htons(0);
SOCKET = socket(AF_INET, SOCK_STREAM, 0);
if (SOCKET == -1)
{
iLastError = errno;
strLastError = "Create socket Error : "+string(strerror(errno));
connected = false;
return connected;
}
struct timeval timeouts, timeoutr;
memset(&timeouts, 0, sizeof(timeouts)); // zero timeout struct before use
timeouts.tv_sec = SendTimeOut/1000;
timeouts.tv_usec = 0;
memset(&timeoutr, 0, sizeof(timeoutr)); // zero timeout struct before use
timeoutr.tv_sec = ReceiveTimeOut/1000;
timeoutr.tv_usec = 0;
int sockopt = setsockopt(SOCKET, SOL_SOCKET, SO_SNDTIMEO, &timeouts, sizeof(timeouts));
if (sockopt == -1)
{
printf("%s%s","Set socket Option error : ",strerror(errno));
iLastError = errno;
strLastError = "setsockopt Error : "+string(strerror(errno));
}
sockopt = setsockopt(SOCKET, SOL_SOCKET, SO_RCVTIMEO, &timeoutr, sizeof(timeoutr)); //
if (sockopt == -1)
{
printf("%s%s","Set socket Option error : ",strerror(errno));
iLastError = errno;
strLastError = "setsockopt Error : "+string(strerror(errno));
}
memset(&sa_loc, 0, sizeof(struct sockaddr_in));
sa_loc.sin_family = AF_INET;
sa_loc.sin_port = htons(0); //8000
sa_loc.sin_addr.s_addr = inet_addr(SourceIP.c_str());
int bindid = bind(SOCKET, (struct sockaddr *)&sa_loc, sizeof(sa_loc));
if (bindid !=0)
{
iLastError = errno;
strLastError = "Bind Error : "+string(strerror(errno));
}
int conn = connect(SOCKET, (struct sockaddr *) &echoserver, sizeof(echoserver));
if (conn == -1)
{
strLastError = "Connect Error : "+string(strerror(errno));
connected = false;
}
else {
connected = true;
}
return connected;
wpp

if your variable SendTimeOut is < 1000 then your recv timeout will be 0, and I'm not sure if that is the same as setting O_NONBLOCK, but if it is then it sounds like this is normal process, and you should loop until it succeeds (or you get EISCONN) or fails with a different error code. If this is intended you should probably just set O_NONBLOCK explicitly.
http://linux.die.net/man/3/connect
EINPROGRESS
O_NONBLOCK is set for the file descriptor for the socket and the connection cannot be immediately established; the connection shall be established asynchronously.
...
If the connection cannot be established immediately and O_NONBLOCK is set for the file descriptor for the socket, connect() shall fail and set errno to [EINPROGRESS], but the connection request shall not be aborted, and the connection shall be established asynchronously. Subsequent calls to connect() for the same socket, before the connection is established, shall fail and set errno to [EALREADY].

Related

C/C++: socket() creation fails in the loop, too many open files

I am implementing a client-server TCP socket application. Client is on an OpenWRT Linux router (C based) and writes some data on the socket repeatedly and in a loop at some frequency rate. The Server is on a Linux Ubuntu machine (C/C++ based) and reads data in a loop according to data arrival speed.
Problem: Running the Server and then Client, server keeps reading new data. Both sides work well until the number of data deliveries (# of connections) reaches 1013. After that, the Client stuck at socket(AF_INET,SOCK_STREAM,0) with socket creation failed...: Too many open files. Apparently, the number of open fd approaches ulimit -n = 1024 on client.
I put the snippets of the code which shows the loop structures for Server.cpp and Client.c:
Server.c:
// TCP Socket creation stuff over here (work as they should):
// int sock_ = socket() / bind() / listen()
while (1)
{
socklen_t sizeOfserv_addr = sizeof(serv_addr_);
fd_set set;
struct timeval timeout;
int connfd_;
FD_ZERO(&set);
FD_SET(sock_, &set);
timeout.tv_sec = 10;
timeout.tv_usec = 0;
int rv_ = select(sock_ + 1, &set, NULL, NULL, &timeout);
if(rv_ == -1){
perror("select");
return 1;
}
else if(rv_ == 0){
printf("Client disconnected.."); /* a timeout occured */
close (connfd_);
close (sock_);
}
else{
connfd_ = accept (sock_,(struct sockaddr*)&serv_addr_,(socklen_t*)&sizeOfserv_addr);
if (connfd_ >= 0) {
int ret = read (connfd_, &payload, sizeof(payload)); /* some payload */
if (ret > 0)
printf("Received %d bytes !\n", ret);
close (connfd_); /* Keep parent socket open (sock_) */
}else{
printf("Server acccept failed..\n");
close (connfd_);
close (stcp.sock_);
return 0;
}
}
}
Client.cpp:
while (payload_exist) /* assuming payload_exist is true */
{
struct sockaddr_in servaddr;
int sock;
if (sock = socket(AF_INET, SOCK_STREAM, 0) == -1)
perror("socket creation failed...\n");
int one = 1;
int idletime = 2;
setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, &one, sizeof(one));
setsockopt(sock, IPPROTO_TCP, TCP_KEEPIDLE, &idletime, sizeof(idletime));
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &one, sizeof(one));
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = inet_addr("192.168.100.12");
servaddr.sin_port = htons(PORT); /* some PORT */
if (connect (sock, (struct sockaddr*)&servaddr, sizeof(servaddr)) != 0){
perror("connect failed...");
return 1;
}
write(sock, (struct sockaddr*)&payload, sizeof(payload)); /* some new payload */
shutdown(sock,SHUT_WR);
bool serverOff = false;
while (!serverOff){
if(read(sock, &res, sizeof(res)) < 0){
serverOff = true;
close(sock);
}
}
}
NOTE: payload is 800 bytes and always gets fully transmitted per one write action. Having both codes defined under int main(), the client keeps creating sockets and sending data, on the other side, server receives all and would automatically close() and leave if client terminates, due to using select(). If I don't terminate the Client, however, by checking some print logs, it is evident that Server successfully receives 1013 payloads before client crashes with socket creation failed...: Too many open files.
Update:
Following the point mentioned by Steffen Ullrich, it turned out that, the client socket fd has no leak, and the existence of a second fd in the original loop (which was left open) was making the ulimit exceed the limit.
if(read(sock, &res, sizeof(res)) < 0){
serverOff = true;
close(sock); /********* Not actually closing sock *********/
}
Your check for end of connection is wrong.
read returns 0 if the other side has shut down the connection and <0 only on error.
if (sock = socket(AF_INET, SOCK_STREAM, 0) == -1)
perror("socket creation failed...\n");
Given the precedence of operators in C this basically says:
sock = ( socket(AF_INET, SOCK_STREAM, 0) == -1) )
if (sock) ...
Assuming that socket(...) will not return an error but a file descriptor (i.e. >=0) the comparison will be false and thus this essentially says sock = 0 while leaking a file descriptor if the fd returned by socket was >0.

TCP Connect With Invalid Connection Blocks Port

I'm writing a TCP communication script in c++ to communicate between my computer and an Aldebaran Nao robot.
In general my script is working. However, the trouble I am having is that when I call connect from the client (when the server application is closed or the ethernet connection removed) I get an error that the operation is in progress.
However, once the server application is restarted / ethernet cable reconnected, I still cannot call connect to successfully reestablish a connection. I still get an error that the operation is in progress.
As a note, whenever my client determines that a connection cannot be made, the socket descriptor is closed before reattempting a connection. Here is my code for connecting on the client side:
If there is any more information that would be useful, I would be happy to provide it. This project is relatively large, so I didn't want to include too much irrelevant information here.
TCPStream* TCPConnector::connect(const char* serverIP, int port, int timeoutSec)
{
if (timeoutSec == 0)
{
return connect(serverIP, port);
}
struct sockaddr_in address;
// Store all zeros for address struct.
memset(&address, 0, sizeof(address));
// Configure address struct.
address.sin_family = AF_INET;
address.sin_port = htons(port); // Convert from host to TCP network byte order.
inet_pton(PF_INET, serverIP, &(address.sin_addr)); // Convert IP address to network byte order.
// Create a socket. The socket signature is as follows: socket(int domain, int type, int protocol)
int sd = socket(AF_INET, SOCK_STREAM, 0);
int optval = 1;
if (setsockopt(sd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof optval) == -1)
{
std::cout << "failed to set socket option" << std::endl;
}
// Set socket to be non-blocking.
int arg;
arg = fcntl(sd, F_GETFL, NULL);
arg |= O_NONBLOCK;
fcntl(sd, F_SETFL, arg);
// Connect with time limit.
fd_set set;
FD_ZERO(&set); // Clear the set.
FD_SET(sd, &set); // Add our file descriptor to the set.
struct timeval timeout;
timeout.tv_sec = timeoutSec;
timeout.tv_usec = 0;
// If the connect call returns 0, then the connection was established. Otherwise,
// check if the three-way handshake is underway.
if (::connect(sd, (struct sockaddr *)&address, sizeof(address)) < 0)
{
// If the handshake is underway.
if (errno == EINPROGRESS)
{
std::cout << "handshake in progress" << std::endl;
// Designate timeout period.
int ret = select(sd + 1, NULL, &set, NULL, &timeout);
std::cout << "return value from select : " << ret << std::endl;
// Check if timeout or an error occurred.
if (ret <= 0)
{
return NULL;
}
else
{
// Check if select returned 1 due to an error.
int valopt;
socklen_t len = sizeof(int);
getsockopt(sd, SOL_SOCKET, SO_ERROR, (void*)(&valopt), &len);
if (valopt)
{
char * errorMessage = strerror( errno); // get string message from errn
std::string msg (errorMessage);
std::cout << msg << std::endl;
return NULL;
}
}
}
else
{
return NULL;
}
}
// Return socket to blocking mode
arg = fcntl(sd, F_GETFL, NULL);
arg &= (~O_NONBLOCK);
fcntl(sd, F_SETFL, arg);
// Create stream object.
return new TCPStream(sd, &address);
}
Your socket is non-blocking mode (you do it explicitly).
As a result, your connect will return immediately with 'connection is in progress'. When socket is non-blocking, you would need than to poll on this socket and wait for it to become readable and/or writeable - this would mean connection is completed (either successfully or not).
A better option in my view would be to use blocking sockets - I see no reason for you to use non-blocking call here.

C++ Reconnect TCP Server to Client after Client restart

I want to implement a 'flexible' TCP connection where I can randomly shutdown and restart both the Server and the Client. The other one should then automatically detect the shutdown and enter try to reconnect. I successfully implemented this s.t. I can shutdown and restart the server. The client discovers the shutdown (via recv(...) == 0) and then closes the connection (it therefore closes the sockets close(this->sockfd_) and close(this->newsockfd_)).
Unfortunately I am not able to get this working the other way around. I initialize the server (using the class constructor) the following way:
tcpServer::tcpServer(int _port) {
this->sockfd_ = -1;
this->port_ = _port;
this->connected_ = false;
if ((this->sockfd_ = socket(AF_INET, SOCK_STREAM, 0)) < 0)
this->dieWithError("ERROR opening Socket");
else
printf("-> Port %d: Socket opened\n", this->port_);
// get rid of "address already in use" error message
int yes = 1;
setsockopt(this->sockfd_, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
/* assign values to the fields of struct sockaddr_in */
bzero((char *) &this->serv_addr_, sizeof(this->serv_addr_));
this->serv_addr_.sin_family = AF_INET;
this->serv_addr_.sin_port = htons(this->port_);
this->serv_addr_.sin_addr.s_addr = INADDR_ANY;
/* bind the socket to an address */
if (bind(this->sockfd_, (struct sockaddr *) &this->serv_addr_, sizeof(this->serv_addr_)) < 0) {
printf("-> Port %d:", this->port_);
this->dieWithError("ERROR on binding");
}
printf("-> Binding successful. Start TCP client in new terminal\n");
fflush(stdout);
/* listen for connections and accept a connection */
listen(this->sockfd_, 5);
this->clilen_ = sizeof(this->cli_addr_);
if ((this->newsockfd_ = accept(this->sockfd_, (struct sockaddr *) &this->cli_addr_, &this->clilen_)) < 0)
this->dieWithError("Error on accept");
else {
printf("-> Connection established\n");
this->connected_ = true;
}
}
So once the server detects that the connection is closed, it enters a loop where it tries to reconnect using the following code:
void tcpServer::connect() {
if (this->sockfd_ == -1) {
/* create socket */
if ((this->sockfd_ = socket(AF_INET, SOCK_STREAM, 0)) < 0)
this->dieWithError("ERROR opening Socket");
else
printf("-> Port %d: Socket opened\n", this->port_);
// get rid of "address already in use" error message
int reuse_address = 1;
setsockopt(this->sockfd_, SOL_SOCKET, SO_REUSEADDR, &reuse_address, sizeof(int));
/* listen for connections and accept a connection */
listen(this->sockfd_, 5);
this->clilen_ = sizeof(this->cli_addr_);
if ((this->newsockfd_ = accept(this->sockfd_, (struct sockaddr *) &this->cli_addr_, &this->clilen_)) < 0)
this->dieWithError("Error on accept");
else {
printf("-> Connection established\n");
this->connected_ = true;
}
}
}
Some simple debugging output tells me that in the reconnect-mode, the server gets stuck in the
accept(this->sockfd_, (struct sockaddr *) &this->cli_addr_, &this->clilen_) call. Another observation I made is that the client does not shut down properly (via ctrl-c), i.e., it gets stuck in a loop somewhere and does not properly close the connection.
Since I am a total beginner with the TCP stuff, I would be very happy if someone could point me to the right direction. Thank you.

blocking sockets timeout on receive issues

I'm writing a MFC\C++ program that needs to create a UDP socket to receive datagrams on.
I am using blocking socket (for performance reasons) and have some errors (or misunderstanding) when trying to set timeout for receive calls.
When I set the receive timeout to 100mili using setsockopt() and the receive does timeout - it timeouts after about 600mili.
When I set the receive timeout to 1000mili using setsockopt() and the receive does timeout - it timeouts after about 1600mili.
Why is this ?
Am I doing something wrong ?
My code goes something like this:
WSADATA wsaData;
SOCKET ReceivingSocket;
SOCKADDR_IN ReceiverAddr;
int Port = 2345;
char ReceiveBuf[1024];
int BufLength = 1024;
SOCKADDR_IN SenderAddr;
int SenderAddrSize = sizeof(SenderAddr);
int Ret;
// 100mili timeout
int RecvTimeout = 100 ;
// Initialize Winsock version 2.2
if ((Ret = WSAStartup(MAKEWORD(2,2), &wsaData)) != 0)
{
TRACE("ERROR: WSAStartup failed with error %d\n", Ret);
return;
}
// Create a new socket to receive datagrams
if ((ReceivingSocket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))
== INVALID_SOCKET)
{
TRACE("ERROR: socket failed with error %d\n", WSAGetLastError());
WSACleanup();
return;
}
// receive datagrams from all interfaces using port 2345
ReceiverAddr.sin_family = AF_INET;
ReceiverAddr.sin_port = htons(Port);
ReceiverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
// bind
if (bind(ReceivingSocket, (SOCKADDR *)&ReceiverAddr, sizeof(ReceiverAddr))
== SOCKET_ERROR)
{
TRACE("ERROR: bind failed with error %d\n", WSAGetLastError());
closesocket(ReceivingSocket);
WSACleanup();
return;
}
// set receive timeout
if ( setsockopt (
ReceivingSocket,
SOL_SOCKET,
SO_RCVTIMEO,
(const char*)&RecvTimeout,
sizeof(RecvTimeout) ) == SOCKET_ERROR )
{
TRACE("Error using setsockopt\n") ;
closesocket(ReceivingSocket);
WSACleanup();
return;
}
// Receive 10 messages - here the timeout comes to life...
for(int i = 0 ; i < 10 ; i++)
{
TRACE("Before Recv, Ticks=%d\n", GetTickCount()) ;
if ((Ret = recvfrom(ReceivingSocket, ReceiveBuf, BufLength, 0,
(SOCKADDR *)&SenderAddr, &SenderAddrSize)) == SOCKET_ERROR)
{
if(WSAETIMEDOUT == WSAGetLastError())
TRACE("After Recv, Ticks=%d\n\n", GetTickCount()) ;
else
{
TRACE("ERROR: receive failed with error %d\n", WSAGetLastError());
closesocket(ReceivingSocket);
WSACleanup();
return;
}
}
}
closesocket(ReceivingSocket);
WSACleanup();
and the output I get is this:
Before Recv, Ticks=1476485406
After Recv, Ticks=1476486031
Before Recv, Ticks=1476486031
After Recv, Ticks=1476486656
Before Recv, Ticks=1476486656
After Recv, Ticks=1476487281
.
.
.
In addition, when I looked at the MSDN to find out more about SO_RCVTIMEO I noticed the following:
If a send or receive operation times out on a socket, the socket state is indeterminate, and should not be used..."
So basically using SO_RCVTIMEO seems like a bad idea if I do get timeouts.
Am I missing something ?
Use 'timeval' stuct to initialize timeout value.
struct timeval timeout;
timeout.tv_sec = SOCKET_READ_TIMEOUT_SEC; // in milli secs
timeout.tv_usec = 0;

Getting "Transport endpoint is not connected" in UDP socket programming in C++

I am getting Transport endpoint is not connected error in UDP server program, while I am try to
shutdown the socket via shutdown(m_ReceiveSocketId, SHUT_RDWR);
Following is my code snippet:
bool UDPSocket::receiveMessage()
{
struct sockaddr_in serverAddr; //Information about the server
struct hostent *hostp; // Information about this device
char buffer[BUFFERSIZE]; // Buffer to store incoming message
int serverlen; // to store server address length
//Open a datagram Socket
if((m_ReceiveSocketId = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
Utility_SingleTon::printLog(LOG_ERROR,"(%s %s %d) UDP Client - socket() error",__FILE__,__func__, __LINE__);
pthread_exit(NULL);
return false;
}
//Configure Server Address.
//set family and port
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(m_ListeningPort);
if (bind(m_ReceiveSocketId, (struct sockaddr *) &serverAddr,sizeof(struct sockaddr_in)) < 0 )
{
Utility_SingleTon::printLog(LOG_ERROR,"(%s %s %d) UDP Client- Socket Bind error=%s",__FILE__,__func__, __LINE__,strerror(errno));
pthread_exit(NULL);
return false;
}
//TODO Re-Route Mechanism.
if((serverAddr.sin_addr.s_addr = inet_addr(m_ServerIPStr.c_str())) == (unsigned long)INADDR_NONE)
{
/* Use the gethostbyname() function to retrieve */
/* the address of the host server if the system */
/* passed the host name of the server as a parameter. */
/************************************************/
/* get server address */
hostp = gethostbyname(m_ServerIPStr.c_str());
if(hostp == (struct hostent *)NULL)
{
/* h_errno is usually defined */
/* in netdb.h */
Utility_SingleTon::printLog(LOG_ERROR,"%s %d %s %s %d", "Host Not found", h_errno,__FILE__,__func__, __LINE__);
pthread_exit(NULL);
return false;
}
memcpy(&serverAddr.sin_addr, hostp->h_addr, sizeof(serverAddr.sin_addr));
}
serverlen = (int )sizeof(serverAddr);
// Loop and listen for incoming message
while(m_RecevieFlag)
{
int receivedByte = 0;
memset(buffer, 0, BUFFERSIZE);
//receive data from the server
receivedByte = recvfrom(m_ReceiveSocketId, buffer, BUFFERSIZE, 0, (struct sockaddr *)&serverAddr, (socklen_t*)&serverlen);
if(receivedByte == -1)
{
Utility_SingleTon::printLog(LOG_ERROR,"[%s:%d#%s] UDP Client - receive error",__FILE__,__LINE__,__func__);
close(m_ReceiveSocketId);
pthread_exit(NULL);
return false;
}
else if(receivedByte > 0)
{
string rMesg;
rMesg.erase();
for(int loop = 0; loop < receivedByte; loop++)
rMesg.append(1, buffer[loop]);
Utility_SingleTon::printLog(LOG_DEBUG,"[%s:%d#%s] received message=%d",__FILE__,__LINE__,__func__, rMesg.length());
QOMManager_SingleTon::getInstance()->setReceivedMessage(rMesg);
raise(SIGUSR1);
}
}
close(m_ReceiveSocketId);
pthread_exit(NULL);
return true;
}
Any help would be appreciated.
Thanks Yuvi.
You don't need to call shutdown() for a UDP socket. From the man page:
The shutdown() call causes all or part of a full-duplex connection on the socket
associated with sockfd to be shut down.
If you call shutdown() on a UDP socket, it will return ENOTCONN
(The specified socket is not connected) because UDP is a connectionless protocol.
All you need to do is close the socket and set the socket to INVALID_SOCKET. Then in your destructor check whether the socket has already been set to INVALID_SOCKET before closing it.