Chat room using socket programming with select() - winsock - C - c

I try to create a server-client application where the server provides a chat service to all clients that connect to the server. The server and client use cryptographic algorithms and protocols to secure data transmitted over the network. I can't figure out why the chat code isn't working properly.
I use the select() function to operate multiple drawers at the same time. If I use only a piece of code when multiple clients connect to the server and send data to the server and it gets everything, that's fine, but as soon as I try to write a piece of code that would be a chat function, even if multiple clients connect, the server serves only the last connected client. I use a link dynamic list to store the necessary client information, and when I can list currently connected clients, if I don't use part of the chat room code, all clients I connect will be accepted, and as soon as I use the chat room code part, only the last connected client.
This is code for server:
while(1) {
fd_set reads;
reads = master;
//The select function determines the status of one or more sockets, waiting if necessary, to perform synchronous I/O
if (select(max_socket+1, &reads, 0, 0, 0) < 0) {
fprintf(stderr, "select() failed. (%d)\n", GETSOCKETERRNO());
return 1;
}
SOCKET i;
//Loop through each possible socket
for(i = 1; i <= max_socket; ++i) {
if (FD_ISSET(i, &reads)) {
//If socket_listen, create TCP connection of accept() function
if (i == socket_listen) {
//
client_info = create_client();
client_info->client_len = sizeof(client_info->client_address);
client_info->sock_fd = accept(socket_listen,
(struct sockaddr*) &client_info->client_address,
&client_info->client_len);
if (!ISVALIDSOCKET(client_info->sock_fd)) {
fprintf(stderr, "accept() failed. (%d)\n",
GETSOCKETERRNO());
return 1;
}
FD_SET(client_info->sock_fd, &master);
if (client_info->sock_fd > max_socket)
max_socket = client_info->sock_fd;
//Prints the client address using the getnameinfo() function
getnameinfo((struct sockaddr*)&client_info->client_address,
client_info->client_len,
client_info->address_buffer,
100, 0, 0,
NI_NUMERICHOST);
printf("New connection %s\n", client_info->address_buffer);
printf("\nWaiting for succeses Salt handshake...\n");
//Salt handshake
salt_hndshk(client_info);
//Insert client to the list of clients
insert(p_list, client_info);
//List of clients connected to the server with a successful Salt handshake
listing_clients(p_list);
} else {
memset(rx_buffer, 0, sizeof(hndsk_buffer));
//Search for clients by sockets and the is in the list
//the server decrypts the data from the client
CLIENT *client_decrypt = create_client();
client_decrypt = search_client(p_list, i);
ret_msg = salt_read_begin_pom(&client_decrypt->channel, rx_buffer,
sizeof(rx_buffer), &msg_in, pom_buffer, &decrypt_size);
//Check if SALT_ERROR from message
if(ret_msg == SALT_ERROR) {
printf("\tThe client disconnects from the server.\n");
printf("\tThe server has closed him socket\n");
realese_client(p_list, client_decrypt);
FD_CLR(i, &master);
CLOSESOCKET(i);
continue;
}
//Freeing client memory
free(client_decrypt);
}
//Chat room service
SOCKET j;
for(j = 1; j <= max_socket; ++j){
if(FD_ISSET(j, &master)){
if (j == socket_listen || j == i){
continue;
} else {
memset(rx_buffer, 0, sizeof(hndsk_buffer));
//Search for clients by sockets and the is in the list
CLIENT *client_encrypt = create_client();
client_encrypt = search_client(p_list, j);
//Prepare data before send
salt_write_begin(tx_buffer, sizeof(tx_buffer), &msg_out);
//Copy clear text message to be encrypted to next encrypted package
salt_write_next(&msg_out, (uint8_t * )pom_buffer, decrypt_size);
//Wrapping, creating encrpted messages
salt_write_execute(&client_encrypt->channel, &msg_out, false);
//Freeing client memory
free(client_encrypt);
}
} //if(FD_ISSET(j, &master)
} //for(j = 1; j <= max_socket; ++j)
//Finish chat room service
} //if FD_ISSET
} //for i to max_socket
}
There is a link to the application on this link:
tcp_salt

You have logic errors in both of your inner for loops.
When reading from/writing to a non-listening client socket, DO NOT call create_client() at all, you are creating memory leaks with it:
CLIENT *client_decrypt = create_client();
client_decrypt = search_client(...); // <-- LEAK!
CLIENT *client_encrypt = create_client();
client_encrypt = search_client(...); // <-- LEAK!
Call create_client() ONLY when you accept() a new client. And DO NOT call free() on any CLIENT you read from/write to. Call that ONLY when you are removing a CLIENT from p_list.
You are corrupting your p_list on each loop iteration, leaving it with a bunch of dangling pointers to invalid CLIENTs.
Also, your writing code is not checking for errors to disconnect and remove dead clients.
Try something more like this:
while(1) {
fd_set reads;
reads = master;
//The select function determines the status of one or more sockets, waiting if necessary, to perform synchronous I/O
if (select(max_socket+1, &reads, 0, 0, 0) < 0) {
fprintf(stderr, "select() failed. (%d)\n", GETSOCKETERRNO());
return 1;
}
//Loop through each possible socket
for(SOCKET i = 1; i <= max_socket; ++i) {
if (!FD_ISSET(i, &master)) {
continue;
}
if (FD_ISSET(i, &reads)) {
//If socket_listen, create TCP connection of accept() function
if (i == socket_listen) {
//
CLIENT *client_info = create_client();
client_info->client_len = sizeof(client_info->client_address);
client_info->sock_fd = accept(socket_listen,
(struct sockaddr*) &client_info->client_address,
&client_info->client_len);
if (!ISVALIDSOCKET(client_info->sock_fd)) {
fprintf(stderr, "accept() failed. (%d)\n",
GETSOCKETERRNO());
return 1;
}
FD_SET(client_info->sock_fd, &master);
if (client_info->sock_fd > max_socket)
max_socket = client_info->sock_fd;
//Prints the client address using the getnameinfo() function
getnameinfo((struct sockaddr*)&client_info->client_address,
client_info->client_len,
client_info->address_buffer,
100, 0, 0,
NI_NUMERICHOST);
printf("New connection %s\n", client_info->address_buffer);
printf("\nWaiting for succesful Salt handshake...\n");
//Salt handshake
salt_hndshk(client_info);
//Insert client to the list of clients
insert(p_list, client_info);
//List of clients connected to the server with a successful Salt handshake
listing_clients(p_list);
continue;
}
memset(rx_buffer, 0, sizeof(rx_buffer));
//Search for clients by sockets and the is in the list
//the server decrypts the data from the client
CLIENT *client_decrypt = search_client(p_list, i);
ret_msg = salt_read_begin_pom(&client_decrypt->channel, rx_buffer,
sizeof(rx_buffer), &msg_in, pom_buffer, &decrypt_size);
//Check if SALT_ERROR from message
if (ret_msg == SALT_ERROR) {
printf("\tThe client disconnects from the server.\n");
printf("\tThe server has closed his socket\n");
release_client(p_list, client_decrypt);
free(client_decrypt);
CLOSESOCKET(i);
FD_CLR(i, &master);
continue;
}
//Chat room service
for(SOCKET j = 1; j <= max_socket; ++j){
if (!FD_ISSET(j, &master) || j == socket_listen || j == i){
continue;
}
memset(rx_buffer, 0, sizeof(rx_buffer));
//Search for clients by sockets and the is in the list
CLIENT *client_encrypt = search_client(p_list, j);
//Prepare data before send
ret_msg = salt_write_begin(tx_buffer, sizeof(tx_buffer), &msg_out);
//Copy clear text message to be encrypted to next encrypted package
if (ret_msg != SALT_ERROR)
ret_msg = salt_write_next(&msg_out, (uint8_t * )pom_buffer, decrypt_size);
//Wrapping, creating encrpted messages
if (ret_msg != SALT_ERROR
ret_msg = salt_write_execute(&client_encrypt->channel, &msg_out, false);
//Check if SALT_ERROR from message
if (ret_msg == SALT_ERROR) {
printf("\tThe client disconnects from the server.\n");
printf("\tThe server has closed his socket\n");
release_client(p_list, client_decrypt);
free(client_decrypt);
CLOSESOCKET(i);
FD_CLR(i, &master);
continue;
}
}
}
}
}

Related

Multiple clients on server with multithreading using Socket Programming in C

I want to write some code using multithreading and sockets to create a server and this server can accept four connections (clients)
How can I receive and send data to the client? How do I know from which client I receive my data?
This the code:
if (listen(serverSocket, 20) == 0)
printf("Listening\n");
else
printf("Error\n");
int i = 0;
while (1){
addr_size = sizeof(serverStorage);
//accept
newSocket = accept(serverSocket,
(struct sockaddr*)&serverStorage,
&addr_size);
int type = 0;
recv(newSocket,
&type, sizeof(type), 0);
if (type == 1) {
// Creater readers thread
if (pthread_create(&readerthreads[i++], NULL,
reader, &newSocket)
!= 0)
// Error in creating thread
printf("Failed to create thread\n");
}
else if (type == 2) {
// Create writers thread
if (pthread_create(&writerthreads[i++], NULL,
writer, &newSocket)
!= 0)
// Error in creating thread
printf("Failed to create thread\n");
}
if (i >= 5) {
// Update i
i = 0;
while (i < 5) {
// Suspend execution of
// the calling thread
// until the target
// thread terminates
pthread_join(writerthreads[i++],
NULL);
pthread_join(readerthreads[i++],
NULL);
}
// Update i
i = 0;
}
}
How can I modify it to receive data from a specific client and send also to specific client?
there is the method send(); and recv(); but I don't know How the variable NewSocket tell to which client is sending it

esp32 idf multi-socket-server

It's my first post so ask for remotely anything if it can help and I didn't provide it.
My application requires multiple sockets being opened at once from Master, then the slaves connect to WiFi, and then to the sockets
Problem is: I have to make it "bulletproof" against constant reconnecting from slaves and i get Accept error:
E (23817) TCP SOCKET: accept error: -1 Too many open files in system
It appears when I reconnect client for 5th time, when Max Number of Open Sockets = 5 in menuconfig,
I disconnect clients from the server when they don't send anything in 1second -> then i assume they got DC-d.
I do it with close() procedure.
void closeOvertimedTask(void * ignore)
{
while(1)
{
for(int i = 0; i < openedSockets;)
{
if(needsRestart[i] == 1)
{
ESP_LOGI("RESTARTING", " task#%d",i);
//lwip_close_r(clientSock[i]);
//closesocket(clientSock[i]);
//ESP_LOGI("closing result", "%d", close(clientSock[i]));
stopSocketHandler(i);
needsRestart[i] = 0;
//if(isSocketOpened[i])
{
}
ESP_LOGI("close", "%d", lwip_close_r(clientSock[i]));
isSocketOpened[i] = 0;
xTaskCreate( handleNthSocket, "TCP_HANDLER", 10*1024, &(sockNums[i]) , tskIDLE_PRIORITY, &socketHandlerHandle[i]);
configASSERT(socketHandlerHandle[i]);
needsRestart[i] = 0;
}
if(isSocketOpened[i])
{
int diff = ((int)((uint64_t)esp_timer_get_time()) - lastWDT[i]) - 2*TCPWDT;
if(diff > 0)
{
if(isSocketOpened[i])
{
ESP_LOGI("I FOUND OUT HE DC-d","");
//closesocket(clientSock[i]);
}
ESP_LOGI("close", "%d", close(clientSock[i]));
stopSocketHandler(i);
isSocketOpened[i] = 0;
xTaskCreate( handleNthSocket, "TCP_HANDLER", 10*1024, &(sockNums[i]) , tskIDLE_PRIORITY, &socketHandlerHandle[i]);
configASSERT(socketHandlerHandle[i]);
}
}
}
}
}
For each socket I run 1 task that is supposed to receive from that socket and act further.
For all of them I have an other task that checks last time a message arrived and restarts tasks when time has exceeded (it's 2 seconds)
I need around 16 sockets opened in the final version so there is no room to have sockets that are still closing after Slave has restarted whole connection
How to properly close a Task with running recv() procedure in it to properly close Socket.
Is there a way to read from Server side that socket has been closed if WiFi hasn't realized STA DC-d
Is this about TIME_WAIT from tcp stack ?
Socket read code:
void handleNthSocket(void * param) // 0 <= whichSocket < openedSockets
{
int whichSocket = *((int *) param);
ESP_LOGI("TCP SOCKET", "%s #%d", getSpaces(whichSocket), whichSocket);
struct sockaddr_in clientAddress;
while (1)
{
if(needsRestart [whichSocket] == 0)
{
socklen_t clientAddressLength = sizeof(clientAddress);
clientSock[whichSocket] = accept(sock[whichSocket], (struct sockaddr *)&clientAddress, &clientAddressLength);
if (clientSock[whichSocket] < 0)
{
ESP_LOGE("TCP SOCKET", "accept error: %d %s", clientSock[whichSocket], strerror(errno)); //HERE IT FLIPS
//E (232189) TCP SOCKET: accept error: -1 Too many open files in system
isSocketOpened[whichSocket] = 0;
needsRestart[whichSocket] = 1;
continue;
}
//isSocketOpened[whichSocket] = 1;
// We now have a new client ...
int total = 1000;
char dataNP[1000];
char *data;
data = &dataNP[0];
for(int z = 0; z < total; z++)
{
dataNP[z] = 0;
}
ESP_LOGI("TCP SOCKET", "%snew client",getSpaces(whichSocket));
ESP_LOGI(" ", "%s#%d connected",getSpaces(whichSocket), whichSocket);
lastWDT[whichSocket] = (uint64_t)esp_timer_get_time() + 1000000;
isSocketOpened[whichSocket] = 1;
// Loop reading data.
while(isSocketOpened[whichSocket])
{
/*
if (sizeRead < 0)
{
ESP_LOGE(tag, "recv: %d %s", sizeRead, strerror(errno));
goto END;
}
if (sizeRead == 0)
{
break;
}
sizeUsed += sizeRead;
*/
ssize_t sizeRead = recv(clientSock[whichSocket], data, total, 0);
/*for (int k = 0; k < sizeRead; k++)
{
if(*(data+k) == '\n')
{
ESP_LOGI("TCP DATA ", "%sthere was enter", getSpaces(whichSocket));
//ESP_LOGI("TIME ", "%d", (int)esp_timer_get_time());
}
//ESP_LOGI("last wdt", "%d", (int)lastWDT[whichSocket]);
}*/
lastWDT[whichSocket] = (uint64_t)esp_timer_get_time();
int diff = ((int)((uint64_t)esp_timer_get_time()) - lastWDT[whichSocket]) - 2*TCPWDT;
ESP_LOGI("last wdt", "%d, data = %s", (int)lastWDT[whichSocket], data);
if(diff > 0)
{
ESP_LOGI("last wdt", "too long - %d", diff);
isSocketOpened[whichSocket] = 0;
}
if (sizeRead < 0)
{
isSocketOpened[whichSocket] = 0;
}
//TODO: all RX from slave routine
for(int k = 0; k < sizeRead; k++)
{
*(data+k) = 0;
}
// ESP_LOGI("lol data", "clientSock[whichSocket]=%d,
/*if(sizeRead > -1)
{
ESP_LOGI("TCP DATA: ", "%c", *(data + sizeRead-1));
}
else
{
ESP_LOGI("TCP DC ", "");
goto END;
}*/
}
if(isSocketOpened[whichSocket])
{
ESP_LOGI("closing result", "%d", close(clientSock[whichSocket]));
}
}
}
}
I don't see you closing your sockets anywhere?
Sockets, no matter the platform, is usually a limited resource, and a resource that will be reused. If you don't close the sockets then the system will think that you still use then, and can't reuse those sockets for new connections (and on POSIX systems even opening files will be affected).
So close connections immediately when they are not needed any more.
Usually this is done by checking what recv and send returns: If they return a value less than zero an error occured and in most cases it's a non-recoverable errors, so connection should be closed. Even if it is a recoverable error, it's easier to close the connection and let the client reconnect.
For recv there's also the special case when it returns zero. That means the other end has closed the connection. That of course you need to close your end as well.
this post solved all my problems
https://www.esp32.com/viewtopic.php?t=911

UNIX Domain socket programming in C, printing issue

I am having a printing issue with my server. I want there to be simultaneous printing when I have 2 or more clients active on terminals. However, I am only printing from one client at a time. Once I close a client, the other clients are free to write to the server. What can I do to fix my problem?
I have tried to fork the printing section, which I think didn't really do anything. (Just realized if I do this, then the select system call is a waste, i'd rather use the select system call) *edit
while(TRUE) {
FD_ZERO(&readfds);
FD_SET(socket1, &readfds);
FD_SET(socket2, &readfds);
FD_SET(socket3, &readfds);
select(socket3+1, &readfds, NULL, NULL, NULL);
//add socket1
if(FD_ISSET(socket1, &readfds)) {
if((client_socket1 = accept(socket1, NULL, NULL)) < 0) {
perror("accept1");
exit(EXIT_FAILURE);
}
printf("New Connection\n");
puts("Welcome message1 sent successfully\n");
}
//add socket2
if(FD_ISSET(socket2, &readfds)) {
if((client_socket2 = accept(socket2, (struct sockaddr *)&addr2, (socklen_t*)&addr2)) < 0) {
perror("accept2");
exit(EXIT_FAILURE);
}
printf("New Connection\n");
puts("Welcome message2 sent successfully\n");
}
//add socket 3
if(FD_ISSET(socket3, &readfds)) {
if((client_socket3 = accept(socket3, (struct sockaddr *)&addr3, (socklen_t*)&addr3)) < 0) {
perror("accept3");
exit(EXIT_FAILURE);
}
printf("New Connection\n");
puts("Welcome message3 sent successfully\n");
}
//print from socket 3
while( (ready = read(client_socket3, buffer, sizeof(buffer))) > 0) {
printf("%s\n", buffer);
}
//print from socket 2
while( (ready = read(client_socket2, buffer, sizeof(buffer))) > 0) {
printf("%s\n", buffer);
}
//print from socket 1
while( (ready = read(client_socket1, buffer, sizeof(buffer))) > 0) {
printf("%s\n", buffer);
}
}
You need to add your client sockets to the fd_set and select statement before attempting to read from them. Also, you should make all your sockets non-blocking. Otherwise, the read call will block until you get data.
Here's a quick fix that uses recv instead of read to read the sockets, but with the async flag of MSG_DONTWAIT.
I didn't see anywhere where you were closing your client sockets or handling errors properly. So I inserted some code as a hint. Also, it's never a good idea to "printf" a buffer of data from a socket directly. Because you never know if the data you received is null terminated. Always null terminate your buffer after you read the data off the socket.
Change this block of code:
//print from socket 3
while( (ready = read(client_socket3, buffer, sizeof(buffer))) > 0) {
printf("%s\n", buffer);
}
To this:
while (1)
{
int result;
result = recv(client_socket3, buffer, sizeof(buffer)-1, MSG_DONTWAIT);
if ((result == -1) &&
((errno == EAGAIN) || (errno==EWOULDBLOCK)) )
{
// no more data available, but could be available later
// use the socket with "select" above to wait for more data
}
else if ((result == -1) || (result == 0))
{
// remote close or unrecoverable error
close(client_socket3);
client_socket3=-1;
}
else
{
// null terminate the buffer before printing
buffer[result] = '\0';
printf("%s\n", buffer);
}
}

telnetting my socket listening port is closing socket

I am new to this website so I do appologize in advance if this question has been answered before though I have searched it before opening it to everyone here.
I am using socket programming in one of my C program. It has server and client modules where sever and client can communicate in both directions. Program is working fine as I am able to send files and messages in both directions.
My server program is using port 3873 and I have confirmed this with netstat -anp | grep 3873
I have observed one weird behaviour with socket especially when I try to connect socket using browser such as http://localhost:3873 or telnet localhost 3873. It immediately closed socket and subsequent 'netstat -anp | grep 3873' output confirms that localhost is no longer listening on the port 3873.
I would really appreciate if someone can shed light on this behavior. Is it expected behavior?
Here is relevant section from the server code: Main program initiate a dedicated thread and calls startFileServerMT, which subsequent calls handleClient to service each client connected to server on the socket
int handleClient(void *ptr){
DEBUG("Inside the %s %s() \n",__FILE__,__func__);
int connectSOCKET;
connectSOCKET = (int ) ptr;
char recvBUFF[4096],sendBUFF[4096];
char *filename;
FILE * recvFILE;
char *header[4096];
while(1){
if( recv(connectSOCKET, recvBUFF, sizeof(recvBUFF), 0) > 0){
if(!strncmp(recvBUFF,"FBEGIN",6)) {
recvBUFF[strlen(recvBUFF) - 2] = 0;
parseArgs(header,recvBUFF);
filename = (char*) strngDup(header[1]);
DEBUG(" About to receive file: %s\n", filename);
}
char *rfile = ALLOC(sizeof(char) * (strlen(This.uploadDIR) + strlen(filename) + 35));
strcpy(rfile,This.uploadDIR);
if (strngLastChar(rfile) == '/'){
strcat(rfile,filename);
}else{
strcat(rfile,"/");
strcat(rfile,filename);
}
DEBUG(" Absolute file is : %s\n", rfile);
recvBUFF[0] = 0;
if ((recvFILE = fopen (rfile,"w" )) == NULL){
LogError("Server could not create file %s on the shared location %s.\n",filename,This.uploadDIR);
}else{
bzero(recvBUFF,4096);
int fr_block_sz, write_sz;
while((fr_block_sz = recv(connectSOCKET, recvBUFF, 512, 0)) > 0 ){
write_sz = fwrite (recvBUFF , sizeof(recvBUFF[0]) , fr_block_sz , recvFILE );
DEBUG(" Received buffer is : %s\n", recvBUFF);
if(write_sz < fr_block_sz){
LogError("Failed writing file %s on the Server shared location.\n",filename);
break;
}
bzero(recvBUFF,4096);
recvBUFF[0] = 0;
if(write_sz == 0 || fr_block_sz != 512 ){
break;
}
}
if(fr_block_sz < 0){
if(errno == EAGAIN){
LogError("Server collection file %s receive timed out.\n",filename);
}else{
LogError("Failed file %s transfer due to error %d\n",filename,errno);
fclose(recvFILE);
FREE(rfile);
// Start - Following code send failed status to client
sprintf(sendBUFF,"FSTATUS:FAILED\r\n");
if (send(connectSOCKET, sendBUFF, sizeof(sendBUFF), 0) >= 0){
DEBUG("File transfer status for file %s sent\n",filename);
}else{
DEBUG("Failed sending transfer status for file %s\n",filename);
return FALSE;
}
// End
close(connectSOCKET);
return FALSE;
}
}
DEBUG("File %s received on OM Server successfully.\n",filename);
// Start - Following code send failed status to client
sprintf(sendBUFF,"FSTATUS:SUCCESS\r\n");
if (send(connectSOCKET, sendBUFF, sizeof(sendBUFF), 0) >= 0){
DEBUG("File transfer status for file %s sent\n",filename);
}else{
DEBUG("Failed sending transfer status for file %s\n",filename);
return FALSE;
}
// End
fclose(recvFILE);
updateTargets(rfile);
FREE(rfile);
close(connectSOCKET);
break;
}
}
else {
LogInfo("Client dropped connection\n");
}
/** End*/
return TRUE;
}
}
int startFileServerMT(){
DEBUG("Inside %s %s() \n",__FILE__,__func__);
int listenSOCKET, connectSOCKET[512],thread_status;
int socketINDEX = 0;
pthread_t clientFileThread[512];
socklen_t clientADDRESSLENGTH[512];
struct sockaddr_in clientADDRESS[512], serverADDRESS;
if((listenSOCKET = socket(AF_INET, SOCK_STREAM, 0)) < 0 ){
LogAbortError("File server could not create socket.\n");
close(listenSOCKET);
return FALSE;
}
serverADDRESS.sin_family = AF_INET;
serverADDRESS.sin_addr.s_addr = htonl(INADDR_ANY);
serverADDRESS.sin_port = htons(This.serverport);
if (bind(listenSOCKET, (struct sockaddr *) &serverADDRESS, sizeof(serverADDRESS)) < 0) {
LogAbortError("File server could not bind socket and will stop server now.\n");
close(listenSOCKET);
This.stopped = TRUE;
return FALSE;
}
if(listen(listenSOCKET, 5) == -1){
LogAbortError("Server failed to listen on port %d and will stop server now.\n",This.serverport);
close(listenSOCKET);
This.stopped = TRUE;
return FALSE;
}else{
LogInfo("Server listening on port %d successfully.\n",This.serverport);
}
clientADDRESSLENGTH[socketINDEX] = sizeof(clientADDRESS[socketINDEX]);
while(TRUE){
// DEBUG(" Inside the file server main loop index[%d].\n",socketINDEX);
connectSOCKET[socketINDEX] = accept(listenSOCKET, (struct sockaddr *) &clientADDRESS[socketINDEX], &clientADDRESSLENGTH[socketINDEX]);
if(connectSOCKET[socketINDEX] < 0){
LogError("Server could not accept connection.\n");
close(listenSOCKET);
return FALSE;
}else
DEBUG(" Another client connected to server socket.\n");
ThreadCreateDetached( &clientFileThread[socketINDEX], handleClient, connectSOCKET[socketINDEX]);
if(socketINDEX=512) {
socketINDEX = 0;
} else {
socketINDEX++;
}
if (This.stopped == TRUE){
close(listenSOCKET);
return TRUE;
}
/** End*/
// return TRUE;
}
close(listenSOCKET);
return TRUE;
}
This is your problem - or at least a part of your problem. It's not only an off-by-one error (connectSOCKET accepts indices from 0-511 inclusive so if you're at 512, you've already written past the end of the connectSOCKET array) but you do an assignment instead of a comparison:
if(socketINDEX=512) { // Error: you are *setting* socketINDEX to 512,
// then immediately *resetting* it back to 0. So
// every new connection overrides the existing
// socket.
socketINDEX = 0;
} else {
socketINDEX++;
}
As a sidenote, you really ought to refactor your code and try to clean it up.

C: Question about Beej's networking guide... Is there an assumption here?

I was just going through the Networking Guide by Beej and am curious about this part of the code (specifically marked with "From here" and "To here"):
// main loop
for(;;) {
read_fds = master; // copy it
if (select(fdmax+1, &read_fds, NULL, NULL, NULL) == -1) {
perror("select");
exit(4);
}
// 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 == listener) {
// handle new connections
addrlen = sizeof remoteaddr;
newfd = accept(listener,
(struct sockaddr *)&remoteaddr,
&addrlen);
if (newfd == -1) {
perror("accept");
} else {
FD_SET(newfd, &master); // add to master set
if (newfd > fdmax) { // keep track of the max
fdmax = newfd;
}
printf("selectserver: new connection from %s on "
"socket %d\n",
inet_ntop(remoteaddr.ss_family,
get_in_addr((struct sockaddr*)&remoteaddr),
remoteIP, INET6_ADDRSTRLEN),
newfd);
}
} else {
// handle data from a client
//----------------- FROM HERE --------------------------
if ((nbytes = recv(i, buf, sizeof buf, 0)) <= 0) {
// got error or connection closed by client
if (nbytes == 0) {
// connection closed
printf("selectserver: socket %d hung up\n", i);
} else {
perror("recv");
}
close(i); // bye!
FD_CLR(i, &master); // remove from master set
//----------------- TO HERE ----------------------------
} else {
// we got some data from a client
for(j = 0; j <= fdmax; j++) {
// send to everyone!
if (FD_ISSET(j, &master)) {
// except the listener and ourselves
if (j != listener && j != i) {
if (send(j, buf, nbytes, 0) == -1) {
perror("send");
}
}
}
}
}
} // END handle data from client
} // END got new incoming connection
} // END looping through file descriptors
} // END for(;;)--and you thought it would never end!
return 0;
Now I know that read doesn't always read "everything" that is to be read on a socket and that it sometimes can return only part of it. In that case, wouldn't this code be incorrect? I mean, after one read, the connection is being closed... Instead, aren't we supposed to have some other mechanism in place? If so, what is the right approach here?
The socket is only going to get closed there if there was an error from recv(), otherwise it'll deal with the data that was read even if it isnt all read. It will then read more out when it loops through again. Pretty sure this is what you're asking?
Yes you would keep reading until you got all the data you expected, obviosuly you need someway of knowing how much to expect - which is why http puts the document size first
Your only calling close when recv() has returned a negative value which means that recv had some sort of error. Notice that the block where you do the close has a comment stating // got error or connection closed by client).
When you actually get some data (the else branch starting with // we got some data from a client), the connection is not being closed.
You are right that you can't assume the data arrives all at one time. Your mistake is in following how the code is working.

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