Client is sending 1 byte of data after every 4 seconds of interval. once its receives the byte it acknowledge with 1 byte.
Some times on send error 10053 is seen.
iResult = recv(sSocket, (char*)recvbuf, 1, 0);
if(iResult > 0)
{
setsockopt(sSocket, SOL_SOCKET, SO_SNDTIMEO, (const char*)&dwTime, 1);
iResult = send(sSocket,(char*)&recvbuf,1,0);
if(iResult <= 0)
{
// WSAgetLasterrror() == 10053
}
}
Let me know if you need more details
Related
I'm newbee in socket program.
I made my server program with good sample program using select function.
It works well about 20,000 connections over.
But, in some case, connection accept twice consequence without
receive data from first socket.
Only data received from second socket connection.
After that, first socket resource cannot release.
FD_SET and FD_ISSET are not working with first socket in case of consequence accept I think.
Working clients are 6.
Before this situation,
accept, receive data, and close socket, accept, rcv
data, close, ...
In case, accept,
accept, receive data from second socket, and close second socket.
Lost first socket connection.
After that, accept function assign second socket descriptor.
What is problem?
How can release fisrt socket?
BR
Paul
My code is as follow:
while(1)
{
//clear the socket set
FD_ZERO (&readfds);
//add master socket to set
FD_SET (sever_socket, &readfds);
max_sd = sever_socket;
//add child sockets to set
for ( i = 0 ; i < MAX_CLIENT ; i ++)
{
//socket descriptor
sd = client_socket [i];
//if valid socket descriptor then add to read list
if (sd > 0)
{
FD_SET( sd , &readfds);
}
//highest file descriptor number, need it for the select function
if(sd > max_sd)
{
max_sd = sd;
}
}
//wait for an activity on one of the sockets , timeout is NULL , so wait indefinitely
activity = select ( max_sd + 1 , &readfds , NULL , NULL , NULL);
if ((activity < 0) && (errno!=EINTR))
{
LOG_F (WARNING, "select error");
}
//If something happened on the master socket, then its an incoming connection
if (FD_ISSET(sever_socket, &readfds))
{
if ((new_socket = accept (sever_socket, (struct sockaddr *) &address, (socklen_t*) &addrlen)) < 0)
{
perror("accept");
exit(EXIT_FAILURE);
}
//inform user of socket number - used in send and receive commands
LOG_F (INFO, "New connection, socket fd is %d, ip is : %s, port : %d",
new_socket, inet_ntoa(address.sin_addr), ntohs(address.sin_port));
//add new socket to array of sockets
for (i = 0; i < MAX_CLIENT; i++)
{
//if position is empty
if( client_socket[i] == 0 )
{
client_socket[i] = new_socket;
LOG_F (INFO, "Adding to list of sockets as %d" , i);
break;
}
}
}
for (i = 0; i < MAX_CLIENT; i++)
{
sd = client_socket[i];
if (FD_ISSET (sd , &readfds))
{
memset (&rcvBuf, 0x00, sizeof(rcvBuf));
if ((fp = fdopen (sd, "r")) == NULL)
{
LOG_F (WARNING, "TCP_SOCKET FD_OPEN Error");
close (sd);
client_socket[i] = 0;
}
else
{
ret = ioctl (sd, FIONREAD, &nread);
if (nread == 0)
{
fclose (fp);
close (sd);
client_socket[i] = 0;
LOG_F (WARNING, "Client disconnected(as %d, fd %d)", i, sd);
}
else
{
len = recv (sd, rcvBuf, nread, 0);
if (len > 0)
{
LOG_F (INFO, "RECV size %d" , len);
...
do_msg_handler ()
}
}
...
I have a functional server code with only TCP connection. Now I want the server to receive from UDP connection. I have used port 2000 for TCP & port 2001 for UDP. Here is a snippet of my code
struct timeval timeout; // timeout for select(), 1ms
timeout.tv_sec = 0;
timeout.tv_usec = 1000;
fd_set master; // master file descriptor list
fd_set read_fds; // temp file descriptor list for select()
int fdmax; // maximum file descriptor number
FD_ZERO(&master); // clear the master and temp sets
FD_ZERO(&read_fds);
// TCP port setup
int sockfd; // listening socket descriptor
int newsockfd; // newly accept()ed socket descriptor
struct sockaddr_storage remoteaddr; // client address
socklen_t addrlen;
char buf_tcp[256]; // buffer for client data
char buf_copy_tcp[256];
int recv_bytes;
char remoteIP[INET6_ADDRSTRLEN];
int yes=1; // for setsockopt() SO_REUSEADDR
int i, k, rv_getaddrinfo, rv_setsockopt, rv_bind, rv_listen, rv_select;
struct addrinfo hints, *servinfo, *ptr;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
rv_getaddrinfo = getaddrinfo(NULL, "2000", &hints, &servinfo);
for(ptr=servinfo; ptr!=NULL; ptr=ptr->ai_next)
{
sockfd = socket(ptr->ai_family, ptr->ai_socktype, ptr->ai_protocol);
rv_setsockopt = setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
rv_bind = bind(sockfd, ptr->ai_addr, ptr->ai_addrlen);
break;
}
if (ptr == NULL)
{
fprintf(stderr, "CLI Server error: failed to bind\n\r");
exit(2);
}
freeaddrinfo(servinfo); // all done with this
rv_listen = listen(sockfd, 10);
////////////////////////////////////////////////////////////////////////////////////////////////
// UDP port setup
int sockfd_udp; // listening socket descriptor
struct sockaddr_storage remoteaddr_udp; // client address
socklen_t addrlen_udp;
char buf_udp[256]; // buffer for client data
char buf_copy_udp[256];
int recv_bytes_udp;
char remoteIP_udp[INET6_ADDRSTRLEN];
int yes_udp=1; // for setsockopt() SO_REUSEADDR
int j, rv_getaddrinfo_udp, rv_setsockopt_udp, rv_bind_udp;
struct addrinfo hints_udp, *servinfo_udp, *ptr_udp;
memset(&hints_udp, 0, sizeof(hints_udp));
hints_udp.ai_family = AF_UNSPEC;
hints_udp.ai_socktype = SOCK_DGRAM;
hints_udp.ai_flags = AI_PASSIVE;
rv_getaddrinfo_udp = getaddrinfo(NULL, "2001", &hints_udp, &servinfo_udp);
for(ptr_udp=servinfo_udp; ptr_udp!=NULL; ptr_udp=ptr_udp->ai_next)
{
sockfd_udp = socket(ptr_udp->ai_family, ptr_udp->ai_socktype, ptr_udp->ai_protocol);
rv_setsockopt_udp = setsockopt(sockfd_udp, SOL_SOCKET, SO_REUSEADDR, &yes_udp, sizeof(int));
rv_bind_udp = bind(sockfd_udp, ptr_udp->ai_addr, ptr_udp->ai_addrlen);
break;
}
if (ptr_udp == NULL)
{
fprintf(stderr, "CLI UDP Server error: failed to bind\n\r");
exit(2);
}
freeaddrinfo(servinfo_udp); // all done with this
//////////////////////////////////////////////////////////////////////////////////////////////////////////
// add the listener to the master set
FD_SET(sockfd, &master);
FD_SET(sockfd_udp, &master);
// keep track of the biggest file descriptor
if(sockfd > sockfd_udp)
fdmax = sockfd; // so far, it's this one
else
fdmax = sockfd_udp; // so far, it's this one
do
{
read_fds = master; // copy it
rv_select = select(fdmax+1, &read_fds, NULL, NULL, &timeout);
// run through the existing connections looking for data to read
for(i=0; i<=fdmax; i++)
{
if (FD_ISSET(i, &read_fds))
{ // we got one!!
if (i == sockfd)
{
// handle new connections
addrlen = sizeof(remoteaddr);
newsockfd = accept(sockfd, (struct sockaddr *)&remoteaddr, &addrlen);
FD_SET(newsockfd, &master); // add to master set
if (newsockfd > fdmax) // keep track of the max
fdmax = newsockfd;
inet_ntop(remoteaddr.ss_family, get_in_addr((struct sockaddr*)&remoteaddr), remoteIP, INET6_ADDRSTRLEN);
fprintf(stdout, "CLI Server: new connection from %s on socket %d\n\r", remoteIP, newsockfd);
}
else if (i == sockfd_udp)
{
// handle new udp connections
addrlen_udp = sizeof(remoteaddr_udp);
recv_bytes_udp = recvfrom(i, buf_udp, sizeof(buf_udp), 0, (struct sockaddr *)&remoteaddr_udp, &addrlen_udp);
inet_ntop(remoteaddr_udp.ss_family, get_in_addr((struct sockaddr*)&remoteaddr_udp), remoteIP_udp, INET6_ADDRSTRLEN);
for(j=0; j<=recv_bytes_udp; j++)
{
if( (buf_udp[k] == '\r') | (buf_udp[k] == '\n') )
buf_udp[k] = '\0';
}
fprintf(stdout, "CLI UDP Server: received %s from connection %s\n\r", buf_udp, remoteIP_udp);
}
else
{ // handle data from a client
if ((recv_bytes = recv(i, buf_tcp, sizeof(buf_tcp), 0)) <= 0)
{ // got error or connection closed by client
if (recv_bytes == 0) // connection closed
{
fprintf(stdout, "CLI Server: socket %d hung up\n\r", i);
}
else
{
perror("CLI Server error: recv");
exit(6);
}
close(i); // bye!
FD_CLR(i, &master); // remove from master set
}
else
{
for(k=0; k<=recv_bytes; k++)
{
if( (buf_tcp[k] == '\r') | (buf_tcp[k] == '\n') )
buf_tcp[k] = '\0';
}
fprintf(stdout, "CLI Server: received %s from socket %d\n\r", buf_tcp, i);
}
} // END handle data from client
} // END got new incoming connection
} // END looping through file descriptors
} while(QUIT);
I am doing error checking at each stage but didn't include it in the snippet. When I compile & run this, I can connect to port 2000 but not to 2001, my Tera term terminal closes with connection refused message. Why is the client not able to connect to port 2001 (UDP socket) but connects to port 2000 (TCP socket). The server just responds to client messages until client enters QUIT.
I have modeled this code from Beej's Guide to Network Programming selectserver.c code.
The program that I wrote above was correct but my understanding of socket programming was not. It was a fluke that I managed to write correct code but thanks to #EJP for having an extended discussion in the comments to clear up my doubt.
My mistake was using Teraterm's TCP client to connect to a UDP server. Both communications are mutually exclusive & hence can't communicate with one another. So I had to use a UDP client. Netcat provides an option of UDP client using netcat -u <ip address> <port>. Then my UDP server was able to receive messages from UDP client.
Another mistake was confusing bind() with connect() in DATAGRAM sockets. A connected DGRAM is when I use connect on both server & client.
I thought the problem was with select(), as I wrongly thought that UDP & TCP sockets can't be used simultaneously in select(). But the above code is how you write a UDP/TCP server for multiple client.
Thanks again to Beej & #EJP
Quoting form this online kernel doc
SO_TIMESTAMPING
Generates timestamps on reception, transmission or both. Supports
multiple timestamp sources, including hardware. Supports generating
timestamps for stream sockets.
Linux supports TCP timestamping, and I tried to write some demo code to get any timestamp for TCP packet.
The server code as below:
//Bind
if( bind(socket_desc,(struct sockaddr *)&server , sizeof(server)) < 0)
{
perror("bind failed. Error");
return 1;
}
puts("bind done");
//Listen
listen(socket_desc , 3);
//Accept and incoming connection
puts("Waiting for incoming connections...");
int c = sizeof(struct sockaddr_in);
client_sock = accept(socket_desc, (struct sockaddr *)&client, (socklen_t*)&c);
if (client_sock < 0)
{
perror("accept failed");
return 1;
}
// Note: I am trying to get software timestamp only here..
int oval = SOF_TIMESTAMPING_RX_SOFTWARE | SOF_TIMESTAMPING_SOFTWARE;
int olen = sizeof( oval );
if ( setsockopt( client_sock, SOL_SOCKET, SO_TIMESTAMPING, &oval, olen ) < 0 )
{ perror( "setsockopt TIMESTAMP"); exit(1); }
puts("Connection accepted");
char buf[] = "----------------------------------------";
int len = strlen( buf );
struct iovec myiov[1] = { {buf, len } };
unsigned char cbuf[ 40 ] = { 0 };
int clen = sizeof( cbuf );
struct msghdr mymsghdr = { 0 };
mymsghdr.msg_name = NULL;
mymsghdr.msg_namelen = 0;
mymsghdr.msg_iov = myiov;
mymsghdr.msg_iovlen = 1;
mymsghdr.msg_control = cbuf;
mymsghdr.msg_controllen = clen;
mymsghdr.msg_flags = 0;
int read_size = recvmsg( client_sock, &mymsghdr, 0);
if(read_size == 0)
{
puts("Client disconnected");
fflush(stdout);
}
else if(read_size == -1)
{
perror("recv failed");
}
else
{
struct msghdr *msgp = &mymsghdr;
printf("msg received: %s \n",(char*)msgp->msg_iov[0].iov_base);// This line is successfully hit.
// Additional info: print msgp->msg_controllen inside gdb is 0.
struct cmsghdr *cmsg;
for ( cmsg = CMSG_FIRSTHDR( msgp );
cmsg != NULL;
cmsg = CMSG_NXTHDR( msgp, cmsg ) )
{
printf("Time GOT!\n"); // <-- This line is not hit.
if (( cmsg->cmsg_level == SOL_SOCKET )
&&( cmsg->cmsg_type == SO_TIMESTAMPING ))
printf("TIME GOT2\n");// <-- of course , this line is not hit
}
}
Any ideas why no timestamping is available here ? Thanks
Solution
I am able to get the software timestamp along with hardware timestamp using onload with solarflare NIC.
Still no idea how to get software timestamp alone.
The link you gave, in the comments at the end, says:
I've discovered why it doesn't work. SIOCGSTAMP only works for UDP
packets or RAW sockets, but does not work for TCP. – Gio Mar 17 '16 at 9:331
it doesn't make sense to ask for timestamps for TCP, because there's
no direct correlation between arriving packets and data becoming
available. If you really want timestamps for TCP you'll have to use
RAW sockets and implement your own TCP stack (or use a userspace TCP
library). – ecatmur Jul 4 '16 at 10:39
This question already has answers here:
why socket on the receiving peer keep receiving '' infinitely when I use "control-c" to close the socket on the sending peer
(2 answers)
Closed 7 years ago.
Questions:
1. why socket recv keeps receiving data in a while loop, even if I don't send any data from sender? isn't recv() a blocking function, I thought it blocks until tcp receives some data; 2. why numbytes = 0 ?
Below is the code, I just post the code of recv() and send(), I think other parts of the code works fine, but if you need all code to debug, please let me know I'll post them, Thanks!
while(1) { //client receiving code
if ((numbytes = recv(sockfd, buf, MAXDATASIZE, 0)) == -1)
perror("recv");
}
buf[numbytes] = '\0';
printf("numbytes is %d\n", numbytes);
printf("client: received '%s'\n", buf);
}
while(1) { //server sending code
char str[100];
sin_size = sizeof their_addr;
new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size);
if (new_fd == -1) {
perror("accept");
continue;
}
inet_ntop(their_addr.ss_family, get_in_addr((struct sockaddr *)&their_addr), s, sizeof s);
printf("server: got connection from %s\n", s);
while(1) {
printf( "Enter a value :");
scanf("%s", str);
if (send(new_fd, str, 50, 0) == -1)
perror("send");
}
}
Below is the screenshot of the result:
Input on the server terminal
Enter a value :123456
Output on the client terminal
numbytes is 0
client: received '12345'
numbytes is 0
client: received '6'
numbytes is 0
client: received ''
numbytes is 0
client: received ''
numbytes is 0
client: received ''
numbytes is 0
client: received ''
numbytes is 0
client: received ''
numbytes is 0
client: received ''
numbytes is 0
client: received ''
numbytes is 0
client: received ''
Because you're ignoring the possibility of a zero return from recv(), which means the peer has closed the connection, which means you must do so too, and stop reading.
I want to send several files from Server to the Client but I'm having a problem.
Server sendfile code:
while ((len = fread(Buffer,1,sizeof(Buffer), fs)) > 0)
{
if((resultEnviar = send(ClientSocket,Buffer,len,0)) < 0){
printf("ERROR: Failed to send file %s.\n", nombreArchivoADescargar.c_str());
break;
}
sumEnviada+=resultEnviar;
}
fclose(fs);
Client receiveFile code:
//shutdown(sock, SD_SEND); ???????
do{
recvVal = recv(sock, Buffer2, sizeof(Buffer2), 0);
if (recvVal <= 0){
printf("Can't read from socket");
recvVal =0;
fclose(fp);
continue;
}else{
int off =0;
do{
int write_sz = fwrite(Buffer2, 1, recvVal, fp);
if (write_sz < 0){
printf("Can't write to file");
fclose(fp);
break;};
if (write_sz == 0) {cout<<endl<<"Nada que copiar"<<endl; break;}
off += write_sz;
}while(off<recvVal);
bzero(Buffer2, 1024);
contador+=off;
}
}while (contador<LongitudArchivo);
cout<<endl<<"Numero de bytes recibidos: "<<contador<<endl<<endl;
printf("Ok received from client!\n");
fclose(fp);
If I don't use the SHUTDOWN(sock, SD_SEND) I don't receive all the expected bytes but if I use it I don't know how to send more files (how to wake up the send part of the socket).
Thanks!
I don't see what shutdown() has to do with it. You should receive all the bytes either way. If you want to send multiple files, you will have to send the length ahead of each one and read exactly that many following bytes from the socket into each target file.
NB If recv() returns zero you should close the socket and break. If it returns -1 you should log the errno, e.g. via perror(), close the socket, and break.