I'm working on a C program to solve the Dining Philosophers' problem. I loop through 500 philosopher state changes, and output each philosophers' status on each interation with the following statement:
printf(" %d> |%s|%s|%s|%s|%s \n", i, get_state(phils[0]), get_state(phils[1]), get_state(phils[2]), get_state(phils[3]), get_state(phils[4]));
For context, here is the function get_state, which converts a numeric philosopher status into a string:
char * get_state(int t) {
if (t == 1)
return " Thinking ";
if (t == 2)
return " Hungry ";
if (t == 3)
return " Eating ";
return "----Error----";
}
My problem is this: every 5-30 lines, one of them will start with the unicode character U+0001. It appears that it is probably being inserted after the \n of the previous line, but I can't tell what causes it at all!
I've provided a screenshot for clarity:
And here is the whole loop:
for (i = 1; i <= MAX; i++) {
silent = 0;
// receive message from child node
for (j = 0; j < PHIL_NO; j++) {
if(phils[j] == EATING) {
count[j]++;
}
lastPhils[j] = phils[j];
};
read(host[READ], &msg, sizeof(msg));
phils[msg.index] = msg.state;
for (j = 0; j < PHIL_NO; j++) {
if (phils[j] == lastPhils[j])
{
silent++;
}
};
printf("%4d> |%s|%s|%s|%s|%s \n", i, get_state(phils[0]), get_state(phils[1]),
get_state(phils[2]), get_state(phils[3]), get_state(phils[4]));
// if message is "hungry"
if (msg.state == HUNGRY) {
state_left = 0;
state_right = 0;
// check if chopsticks are available
if (phils[(msg.index - 1)%PHIL_NO] == EATING) {
state_left = 1;
}
if(phils[(msg.index + 1)%PHIL_NO] == EATING) {
state_right = 1;
}
// if available...
if (state_left+state_right == 0) {
// send message EATING to node
msg.state = EATING;
write(node[msg.index][WRITE], &msg, sizeof(msg));
} else {
// make the node wait
write(node[msg.index][WRITE], &msg, sizeof(msg));
}
} else if (msg.state == THINKING) {
// awake neighborhood nodes to eat
write(node[(msg.index-1)%PHIL_NO][WRITE], &msg, sizeof(msg));
write(node[(msg.index+1)%PHIL_NO][WRITE], &msg, sizeof(msg));
}
};
Edit: Oddly enough, when I run it in XTerm I can't see the extra character. I think that just means that XTerm doesn't display it. At this point, I'm pretty sure #Barmar is right in assuming it's one of my pipe write()s misbehaving.
Related
Hi I have a C programme that is basacally suppose to simulate the pipe function in linux and write the amount of bytes that are read in a .txt file so
./a.out cat test : grep -v le : wc -l
The problem that I'm trying to figure out is
Why is the same amount of bytes written in the file since I know each process returns a different amount ?
This piece of code is executed in the parent and is trying to count the amount of bytes of each output with a read syscall and writes the output in a write syscall in the next process so that the next process can use the output as his input.
So let's say I have these pipes a | b | c
This code will read the output of a and write it in b so that b can use it as it's input and so on.
for (int i = 1; i < processes-1; i++) {
close(apipe[i][1]);
char str[4096];
int count=0;
int nbChar=0;
while(1){
count=read(apipe[i][0],str,sizeof(str));
nbChar+=count;
if(count==-1){
if (errno == EINTR) {
continue;
} else {
perror("read");
exit(1);
}
}else if(count==0)break;
}
char *leInput=(char*)malloc(nbChar*sizeof(char));
strncpy(leInput,str,nbChar);
if(i>0){
fprintf(fp, "%d : %d \n ", i,nbChar);
}
close(apipe[i][0]);
write(apipe[i+1][1], leInput, nbChar);
}
Each time through the while(1) loop you're read into the beginning of str, not where you left off in the previous iteration. So you're overwriting the previous read with the next read.
You should copy incrementally to leInput each time through the loop. You can then use realloc() to grow it to accomodate the new input, and you can use leInput + nbChar to copy after the place where you finished the previous time.
for (int i = 1; i < processes-1; i++) {
close(apipe[i][1]);
int nbChar=0;
char *leInput = NULL;
while(1){
int count=0;
char str[4096];
count=read(apipe[i][0],str,sizeof(str));
if(count==-1){
if (errno == EINTR) {
continue;
} else {
perror("read");
exit(1);
}
} else if(count==0) {
break;
}
leInput = realloc((nbChar + count)*sizeof(char));
memcpy(leInput + nbChar, str, count);
nbChar += count;
}
if(i>0){
fprintf(fp, "%d : %d \n ", i,nbChar);
}
close(apipe[i][0]);
write(apipe[i+1][1], leInput, nbChar);
}
Alternatively you could just write to the next pipe in the inner loop, without collectiong everything into leInput:
for (int i = 1; i < processes-1; i++) {
int nbChar = 0;
close(apipe[i][1]);
while(1){
int count=0;
char str[4096];
count=read(apipe[i][0],str,sizeof(str));
if(count==-1){
if (errno == EINTR) {
continue;
} else {
perror("read");
exit(1);
}
} else if(count==0) {
break;
}
write(apipe[i+1][1], str, count);
nbChar += count;
}
if(i>0){
fprintf(fp, "%d : %d \n ", i,nbChar);
}
close(apipe[i][0]);
close(apipe[i+1][1])
}
I have a word guessing game which I needs to repeat until the user types Q:. Generally, the answer is in a format A: answer. The game's using sockets!
Instead of while(1), I tried using while(buffer[0]!='Q') but that does not seem to work.
How do I keep making the client play the game?
Additionally, I also need to tell the user how many games he passed correctly?
while (1)
{
FD_ZERO(&readfds);
FD_SET(server_fd, &readfds);
int max_fd = server_fd;
for (int i = 0; i < NUMCLIENT; i++)
{
file_descriptor = client_sockets[i];
if (file_descriptor > 0)
{
FD_SET(file_descriptor, &readfds);
}
if (file_descriptor > max_fd)
{
max_fd = file_descriptor;
}
}
int return_value = select(max_fd + 1, &readfds, NULL, NULL, NULL);
if (return_value == -1)
{
printf("Select Error\n");
}
if (FD_ISSET(server_fd, &readfds))
{
if ((new_socket = accept(server_fd, (struct sockaddr *) &address,
(socklen_t*) &addrlen)) < 0)
{
perror("accept");
}
send(new_socket, greetings[0], strlen(greetings[0]), 0);
send(new_socket, greetings[1], strlen(greetings[1]), 0);
for (int i = 0; i < NUMCLIENT; i++)
{
if (client_sockets[i] == 0)
{
my_fortune(i);
client_sockets[i] = new_socket;
send(new_socket, client_challenges->question, strlen(client_challenges->question), 0);
break;
}
}
}
for (int i = 0; i < NUMCLIENT; i++)
{
file_descriptor = client_sockets[i];
if (file_descriptor == 0)
{
continue;
}
if (FD_ISSET(file_descriptor, &readfds))
{
memset(buffer, 0, 1024);
valread = read(file_descriptor, buffer, 1024);
if (valread == 0)
{
close(file_descriptor);
client_sockets[i] = 0;
continue;
}
printf("%s\n", buffer);
if (buffer[0] == 'A')
{
if (strlen(client_challenges->answer) == (strlen(buffer) - 4))
{
char store[100];
for (int i = 1; i <= strlen(client_challenges->answer); i++)
{
store[i - 1] = buffer[2 + i];
}
store[strcspn(store, "\r\n")] = 0;
if (strcmp(store, client_challenges->answer) == 0)
{
send(file_descriptor, correct, strlen(correct), 0);
//printf("O: Congratulation - challenge passed!\n");
}
else
{
send(file_descriptor, wrong, strlen(wrong), 0);
send(file_descriptor, client_challenges->answer, strlen(client_challenges->answer), 0);
}
//printf("Wrong guess - expected: %s",client_challenges->answer);}
}
else
{
send(file_descriptor, wrong, strlen(wrong), 0);
send(file_descriptor, client_challenges->answer, strlen(client_challenges->answer), 0);
}
//{printf("Wrong guess - expected: %s",client_challenges->answer);}
}
else if (buffer[0] == 'Q')
{
send(file_descriptor, ending, strlen(ending), 0);
exit(1);
}
else
{
send(file_descriptor, error, strlen(error), 0);
exit(1);
}
}
}
}
If there will only be 1 client, you can simply do
// Actual function to start the game
int play() {
int run = 1;
while (run) {
// run the game
// if game over,
run = 0;
}
return 0; // indicate the game ends gracefully
}
int main(int argc, char** argv) {
int run = 1;
int playAgain = 0;
while (run) {
if (play()) {
// Error: the game ends ungracefully
}
// Prompt for play again
if (!playAgain) {
run = 0;
}
}
// Bye
}
The reason is that the variable run is used to control the game flow. If the user quits or something went wrong, you can set run to 0 and the game will stop running.
If there are going to be multiple clients, you might want to have a look at pthread. Every time you receive a new connection, you can create a new thread with pthread_create and set the play function as start_routine and the fd as the argument. For example, you can try
int MAX_CLIENT = 5;
struct pthread_args {
int fd;
};
void* play(void* arg) {
struct pthread_args* args = (struct pthread_args*)arg;
int fd = args->fd;
// Start the game
}
int main(int argc, char** argv) {
pthread_t pth[MAX_CLIENT];
struct pthread_args pth_args;
int new_fd;
int i = 0;
while(1) { // The server continuously receive connections
// Accept connections
new_fd = accept(/*...*/)
if (new_fd < 0) {
// Error: accepting new connection
}
pth_args.fd = new_fd;
int r = pthread_create(&pth[i], NULL, play, &pth_args);
if (!r) {
// Error: creating thread
}
++i;
}
}
PS: You may want to have a look at pthread_detach as well.
Instead of while(1), I tried using while(buffer[0]!='Q') but that does not seem to work.
The reason while(buffer[0] == 'Q') doesn't work is because by the time the while check for the condition, the buffer (assuming it was declared outside of the while loop) might not be the same buffer anymore because you are looping over all clients and save the buffers from clients to the same buffer variable. So if there are 2 clients and the first client says 'Q' and the second client says 'A', the while sees buffer[0] as 'A' instead of 'Q' and hence continuing the game.
Also, I don't think exit(1) in else if (buffer[0] == 'Q') is a good idea. It kills the server and all clients will be forced to quit the game. Just remove the particular client from the client_sockets array.
:) Hope it helps
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
I'm trying to send SMS via MC7304 modem programatically in C++. For AT command, linux share /dev/ttyUSB1 port. Here is my code:
fd_set readSet, writeSet;
struct timeval timeval;
int cellFd = open("/dev/ttyUSB1", O_RDWR, 0);
writeSet = readSet;
timeval.tv_sec = 0;
timeval.tv_usec = 3000000;
int n = 0;
int written = 0;
int readed = 0;
int totalRead = 0;
char buffer[1001];
memset(buffer, '\0', 1001);
written = write(cellFd, "AT+CMGF=1\r\n", 11);
printf("AT+CMGF=1 command sent with result: %d. Waiting for response...\n", written);
while(true)
{
FD_ZERO(&readSet);
FD_SET(cellFd, &readSet);
timeval.tv_sec = 2;
timeval.tv_usec = 0;
n = select(cellFd + 1, &readSet, &writeSet, NULL, &timeval);
if(n == 0)
{
break;
}
else if(n > 0)
{
readed = read(cellFd, buffer + totalRead, 1000 - totalRead);
totalRead += readed;
}
else
{
printf("Error\n");
exit(0);
}
}
if(totalRead > 0)
{
cout << buffer << endl;
}
else
{
printf("No data received\n");
}
totalRead = 0;
readed = 0;
memset(buffer, '\0', 1001);
written = write(cellFd, "AT+CSCS=\"GSM\"\r\n", 15);
printf("AT+CSCS=\"GSM\" command sent with result: %d. Waiting for response...\n", written);
while(true)
{
FD_ZERO(&readSet);
FD_SET(cellFd, &readSet);
timeval.tv_sec = 2;
timeval.tv_usec = 0;
n = select(cellFd + 1, &readSet, &writeSet, NULL, &timeval);
if(n == 0)
{
break;
}
else if(n > 0)
{
readed = read(cellFd, buffer + totalRead, 1000 - totalRead);
totalRead += readed;
}
else
{
printf("Error\n");
exit(0);
}
}
if(totalRead > 0)
{
cout << buffer << endl;
}
else
{
printf("No data received\n");
}
totalRead = 0;
readed = 0;
memset(buffer, '\0', 1001);
written = write(cellFd, "AT+CMGS=\"MY_NUMBER\"\r\n", 24);
printf("AT+CMGS=\"+MY_NUMBER\" command sent with %d result. Waiting for response...\n", written);
while(true)
{
FD_ZERO(&readSet);
FD_SET(cellFd, &readSet);
timeval.tv_sec = 3;
timeval.tv_usec = 0;
n = select(cellFd + 1, &readSet, &writeSet, NULL, &timeval);
if(n == 0)
{
printf("No data\n");
break;
}
else if(n > 0)
{
memset(buffer, '\0', 1001);
readed = read(cellFd, buffer, 1000);
for(int i=0; i<readed; i++)
{
printf("%02x ", buffer[i]);
}
printf("\n");
cout << buffer << endl;
if((*(buffer) == 0x3E) && (*(buffer + 1) == 0x20) && (*(buffer + 2) == 0x0A))
{
written = write(cellFd, "Test\x1A", 5);
printf("SMS text sent with %d result. Waiting for response...\n", written);
}
}
else
{
printf("Error\n");
exit(0);
}
}
The first two commands work fine and returning 'OK' response. Unfortunetly, after sending AT+CMGS command, modem response with 0x0A (line feed) twice, next responsing with 0x3E 0x20 0x0A (> ) (that looks ok). After this sequence, i'm sending text that ends with 0x1A (CTRL-Z), but modem still responding with >. This situation repeats hundreds of times and at the end I got error +CMS ERROR: 305. It looks like:
root#Moxa:/home/SMS# ./SMS
AT+CMGF=1 command sent with result: 11. Waiting for response...
OK
AT+CSCS="GSM" command sent with result: 15. Waiting for response...
OK
AT+CMGS="(SOME NUMBER)" command sent with 24 result. Waiting for response...
>
SMS text sent with 5 result. Waiting for response...
>
[ situation repeats ]
SMS text sent with 5 result. Waiting for response...
+CMS ERROR: 305
What's wrong with this code, how can I fix it?
I have server client application.
When I'm sending messages in a row(without scanf in the code below), it's seems the server doesn't get them(doesn't print).
if I wait a little bit(with the scanf in the code below) and then send the next message the server works fine and prints all messages.
what's the problem?
how can I fix it, cause I want to do more with the message(not just to print it) that arrived to the server.
in my client code(where server prints nothing)
char message[(100)] = {0};
int x = rand();
while(i < 3)
{
printf(" I send %d\n", x);fflush(NULL);
sprintf(message, "%d",x);
if( send(mainSockfd, message,strlen(message),0) == -1)
{
printf("ERRRRRORRRR\n");fflush(NULL);
}
i++;
x = rand() % 100;
}
in my client code(when server prints the messages)
char message[(100)] = {0};
int x = rand();
while(i < 3)
{
printf(" I send %d\n", x);fflush(NULL);
sprintf(message, "%d",x);
if( send(mainSockfd, message,strlen(message),0) == -1)
{
printf("ERRRRRORRRR\n");fflush(NULL);
}
i++;
x = rand() % 100;
scanf("%d",&x); // this is the only change
}
in my server code
char command[(100+1)] = {0};
while(1)
{
readLength = recv(sockfd, command, 100+1,0);
if(readLength > 0)
{
printf("arrived = %s,\n",command);fflush(NULL);
ZeroMemory(command, sizeof(command));
}
else if( readLength == 0)
{
break;
}
else if ( readLength < 0 ){
if(GetLastError() == 10035)
{
continue;
}
if(GetLastError() == 10057 || GetLastError() == 10054)
{
break;
}
continue;
}
}
As you seem to be transferring 0-terminated "strings" without the 0 termination, you should read one char less then the read buffer provides to always have the read buffer being 0-terminated, as if you try to printf a non 0-terminated "string" you provoke undefined behaviour.
So change this
readLength = recv(sockfd, command, 100+1,0);
to become this
readLength = recv(sockfd, command, 100,0);