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[英]Network programming in C (data is not being sent from client to server using send())
[英]C language, using structs to send data from client to server
我必須創建一個客戶端和服務器,客戶端將在其中發送一個字符和一個整數(使用結構),然后我的客戶端會將字母迭代 n(整數)次並將其發送回客戶端。
例如:a 和 4 從客戶端發送,服務器將操作並將 4 個 a 的字符串(aaaa)發送回客戶端。
我知道我真的很接近獲得代碼,但是一旦我發送了我的 char 和 int,我就會收到“分段錯誤(核心轉儲)錯誤”。 我已經完成了我的研究,並且由於缺少強制轉換、在不應該訪問的地方訪問了內存或者指針可能為空而出現錯誤。
代碼如下:
客戶:
// ClientTest.c
// opens fifo1 for writing and fifo2 for reading
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
struct problem {
char letter[1];
int number[1];
};
main (void)
{
struct problem x=0; //Initializing structure to null
int fda; // to write to character server
int fdb; // to read response from character server
int i; // for the iteration
printf("Client: Please enter a character: ");
scanf("%c", &x.letter[0]);
printf("Client: Please enter an integer: ");
scanf("%d", &x.number[0]);
memset(&x.letter, 0, 1);
memset(&x.number, 0, 1);
if((fda=open("FIFO1", O_WRONLY))<0)//opening and validating fifos
printf("cant open fifo to write");
if((fdb=open("FIFO2", O_RDONLY))<0)
printf("cant open fifo to read");
write(fda, x.number, 1);
printf("\nClient: Got the integer sent, now waiting for response ");
//sleep(0.250);
write(fda, x.letter, 1);
printf("\nClient: Got the character sent, now waiting for response ");
char outletter[7];
read(fdb, outletter, 7);
printf("\nClient: received characters from server %c", outletter);
close(fda);
close(fdb);
printf ("\nall done!\n");
}
服務器
// ServerTest.c
// makes 2 fifos named fifo1 and fifo2
// opens fifo1 for reading and fifo2 for writing
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
struct problem {
char letter[1]; // struct to store the character
int number [1]; // struct to store the integer
};
main (void)
{
struct problem x;
int fda; // to read from client char
int fdb; // to write to client char
int finish; // lets me know that client is done
int i; // because C needs this defined as int
int p;
char outletter[7];
memset(&x.letter, 0, 7);
memset(&x.number, 0, 1);
/* Create the fifos and open them */
if ((mkfifo("FIFO1",0666)<0 && errno != EEXIST))
{
perror("cant create FIFO1");
exit(-1);
}
if ((mkfifo("FIFO2",0666)<0 && errno != EEXIST))
{
perror("cant create FIFO2");
exit(-1);
}
if((fda=open("FIFO1", O_RDONLY))<0)
printf("cant open fifo to write");
if((fdb=open("FIFO2", O_WRONLY))<0)
printf("cant open fifo to read");
read(fda, x.letter, 1); //read the character
read(fda, x.number, 1); //read the integer
printf("\nServer: just got character: , %c", x.letter[0]);
printf("\nServer: just got integer: , %d", x.number[0]);
p=x.number[0]-'0';
for( i = 0; i<=p; i++) // iteration to create the character's string
outletter[p] = x.letter[0];
printf("iteration: %d and character: %c\n", i, outletter[0]); // validating the character and integer received
printf("\nServer: outchar is, %s", outletter); // this shows the character to be sent back to client
write(fdb, outletter, p);
printf("\nServer: Got the characters sent: %s", outletter ); // this sends the letter back to client
if(finish == 1)
printf("\nServer: This says I am ready to close ");
close(fda);
close(fdb);
unlink("FIFO1");
unlink("FIFO2");
}
你的代碼有很多問題,我已經讓它運行了,但你仍然可以改進它。
客戶:
// ClientTest.c
// opens fifo1 for writing and fifo2 for reading
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
struct problem {
char letter[1];
int number[1];
};
main (void)
{
struct problem x;
int fda; // to write to character server
int fdb; // to read response from character server
int i; // for the iteration
memset(&x, 0, sizeof(struct problem)) ;
printf("Client: Please enter a character: ");
scanf("%c", x.letter);
printf("Client: Please enter an integer: ");
scanf("%d", x.number);
// removed or else the letter and number would be reverted to zero
// memset(&x.letter, 0, sizeof(char));
// memset(&x.number, 0, sizeof(int));
if((fda=open("FIFO1", O_WRONLY))<0)//opening and validating fifos
printf("cant open fifo to write");
if((fdb=open("FIFO2", O_RDONLY))<0)
printf("cant open fifo to read");
write(fda, x.letter, sizeof(char));
printf("\nClient: Got the character sent, now waiting for response ");
write(fda, x.number, sizeof(int));
printf("\nClient: Got the integer sent, now waiting for response ");
//sleep(0.250);
char outletter[7];
read(fdb, outletter, 7);
printf("\nClient: received characters from server:") ;
printf("%s\n", outletter);
close(fda);
close(fdb);
printf ("\nall done!\n");
}
服務器:
// ServerTest.c
// makes 2 fifos named fifo1 and fifo2
// opens fifo1 for reading and fifo2 for writing
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <fcntl.h>
struct problem {
char letter[1]; // struct to store the character
int number[1]; // struct to store the integer
};
main (void)
{
struct problem x;
int fda; // to read from client char
int fdb; // to write to client char
int finish; // lets me know that client is done
int i; // because C needs this defined as int
int p;
char outletter[7];
memset(x.letter, 0, sizeof(char));
memset(x.number, 0, sizeof(int));
/* Create the fifos and open them */
if ((mkfifo("FIFO1",0666)<0 && errno != EEXIST))
{
perror("cant create FIFO1");
exit(-1);
}
if ((mkfifo("FIFO2",0666)<0 && errno != EEXIST))
{
perror("cant create FIFO2");
exit(-1);
}
if((fda=open("FIFO1", O_RDONLY))<0)
printf("cant open fifo to write");
if((fdb=open("FIFO2", O_WRONLY))<0)
printf("cant open fifo to read");
read(fda, x.letter, sizeof(char)); //read the character
read(fda, x.number, sizeof(int)); //read the integer
printf("\nServer: just got character: , %c", x.letter[0]);
printf("\nServer: just got integer: , %d", x.number[0]);
p=x.number[0];
if (p > 6) p = 6; // Cannot write more than 6 characters in outletter
for( i = 0; i<=p; i++) { // iteration to create the character's string
outletter[i] = x.letter[0];
printf("iteration: %d and character: %c\n", i, outletter[i]); // validating the character and integer received
}
outletter[p] = '\0'; // the string must finish with '\0'
printf("\nServer: outchar is, %s", outletter); // this shows the character to be sent back to client
write(fdb, outletter, p);
printf("\nServer: Got the characters sent: %s", outletter ); // this sends the letter back to client
if(finish == 1)
printf("\nServer: This says I am ready to close ");
close(fda);
close(fdb);
unlink("FIFO1");
unlink("FIFO2");
}
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