linux發送消息
1. linux下c的兩個進程如何實現通信一個進程給另一個進程發送消息，另一個接受並顯示出來。求大神啊
linux中的進程通信分為三個部分：低級通信，管道通信和進程間通信IPC（inter process communication）。linux的低級通信主要用來傳遞進程的控制信號——文件鎖和軟中斷信號機制。linux的進程間通信IPC有三個部分——①信號量，②共享內存和③消息隊列。以下是我編寫的linux進程通信的C語言實現代碼。操作系統為redhat9.0，編輯器為vi，編譯器採用gcc。下面所有實現代碼均已經通過測試，運行無誤。
一.低級通信--信號通信
signal.c
#include <signal.h>
#include <stdio.h>
#include <unistd.h>
/*捕捉到信號sig之後，執行預先預定的動作函數*/
void sig_alarm(int sig)
{
printf("---the signal received is %d. /n", sig);
signal(SIGINT, SIG_DFL); //SIGINT終端中斷信號，SIG_DFL：恢復默認行為，SIN_IGN：忽略信號
}
int main()
{
signal(SIGINT, sig_alarm);//捕捉終端中斷信號
while(1)
{
printf("waiting here!/n");
sleep(1);
}
return 0;
}
二.管道通信
pipe.c
#include <stdio.h>
#define BUFFER_SIZE 30
int main()
{
int x;
int fd[2];
char buf[BUFFER_SIZE];
char s[BUFFER_SIZE];
pipe(fd);//創建管道
while((x=fork())==-1);//創建管道失敗時，進入循環
/*進入子進程，子進程向管道中寫入一個字元串*/
if(x==0)
{
sprintf(buf,"This is an example of pipe!/n");
write(fd[1],buf,BUFFER_SIZE);
exit(0);
}
/*進入父進程，父進程從管道的另一端讀出剛才寫入的字元串*/
else
{
wait(0);//等待子進程結束
read(fd[0],s,BUFFER_SIZE);//讀出字元串，並將其儲存在char s[]中
printf("%s",s);//列印字元串
}
return 0;
}
三.進程間通信——IPC
①信號量通信
sem.c
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/sem.h>
/*聯合體變數*/
union semun
{
int val; //信號量初始值
struct semid_ds *buf;
unsigned short int *array;
struct seminfo *__buf;
};
/*函數聲明，信號量定義*/
static int set_semvalue(void); //設置信號量
static void del_semvalue(void);//刪除信號量
static int semaphore_p(void); //執行P操作
static int semaphore_v(void); //執行V操作
static int sem_id; //信號量標識符
int main(int argc, char *argv[])
{
int i;
int pause_time;
char op_char = 'O';
srand((unsigned int)getpid());
sem_id = semget((key_t)1234, 1, 0666 | IPC_CREAT);//創建一個信號量,IPC_CREAT表示創建一個新的信號量
/*如果有參數，設置信號量，修改字元*/
if (argc > 1)
{
if (!set_semvalue())
{
fprintf(stderr, "Failed to initialize semaphore/n");
exit(EXIT_FAILURE);
}
op_char = 'X';
sleep(5);
}
for(i = 0; i < 10; i++)
{
/*執行P操作*/
if (!semaphore_p())
exit(EXIT_FAILURE);
printf("%c", op_char);
fflush(stdout);
pause_time = rand() % 3;
sleep(pause_time);
printf("%c", op_char);
fflush(stdout);
/*執行V操作*/
if (!semaphore_v())
exit(EXIT_FAILURE);
pause_time = rand() % 2;
sleep(pause_time);
}
printf("/n%d - finished/n", getpid());
if (argc > 1)
{
sleep(10);
del_semvalue(); //刪除信號量
}
exit(EXIT_SUCCESS);
}
/*設置信號量*/
static int set_semvalue(void)
{
union semun sem_union;
sem_union.val = 1;
if (semctl(sem_id, 0, SETVAL, sem_union) == -1)
return(0);
return(1);
}
/*刪除信號量*/
static void del_semvalue(void)
{
union semun sem_union;
if (semctl(sem_id, 0, IPC_RMID, sem_union) == -1)
fprintf(stderr, "Failed to delete semaphore/n");
}
/*執行P操作*/
static int semaphore_p(void)
{
struct sembuf sem_b;
sem_b.sem_num = 0;
sem_b.sem_op = -1; /* P() */
sem_b.sem_flg = SEM_UNDO;
if (semop(sem_id, &sem_b, 1) == -1)
{
fprintf(stderr, "semaphore_p failed/n");
return(0);
}
return(1);
}
/*執行V操作*/
static int semaphore_v(void)
{
struct sembuf sem_b;
sem_b.sem_num = 0;
sem_b.sem_op = 1; /* V() */
sem_b.sem_flg = SEM_UNDO;
if (semop(sem_id, &sem_b, 1) == -1)
{
fprintf(stderr, "semaphore_v failed/n");
return(0);
}
return(1);
}
②消息隊列通信
send.c
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
#define MAX_TEXT 512
/*用於消息收發的結構體--my_msg_type：消息類型，some_text：消息正文*/
struct my_msg_st
{
long int my_msg_type;
char some_text[MAX_TEXT];
};
int main()
{
int running = 1;//程序運行標識符
struct my_msg_st some_data;
int msgid;//消息隊列標識符
char buffer[BUFSIZ];
/*創建與接受者相同的消息隊列*/
msgid = msgget((key_t)1234, 0666 | IPC_CREAT);
if (msgid == -1)
{
fprintf(stderr, "msgget failed with error: %d/n", errno);
exit(EXIT_FAILURE);
}
/*向消息隊列中發送消息*/
while(running)
{
printf("Enter some text: ");
fgets(buffer, BUFSIZ, stdin);
some_data.my_msg_type = 1;
strcpy(some_data.some_text, buffer);
if (msgsnd(msgid, (void *)&some_data, MAX_TEXT, 0) == -1)
{
fprintf(stderr, "msgsnd failed/n");
exit(EXIT_FAILURE);
}
if (strncmp(buffer, "end", 3) == 0)
{
running = 0;
}
}
exit(EXIT_SUCCESS);
}
receive.c
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/msg.h>
/*用於消息收發的結構體--my_msg_type：消息類型，some_text：消息正文*/
struct my_msg_st
{
long int my_msg_type;
char some_text[BUFSIZ];
};
int main()
{
int running = 1;//程序運行標識符
int msgid; //消息隊列標識符
struct my_msg_st some_data;
long int msg_to_receive = 0;//接收消息的類型--0表示msgid隊列上的第一個消息
/*創建消息隊列*/
msgid = msgget((key_t)1234, 0666 | IPC_CREAT);
if (msgid == -1)
{
fprintf(stderr, "msgget failed with error: %d/n", errno);
exit(EXIT_FAILURE);
}
/*接收消息*/
while(running)
{
if (msgrcv(msgid, (void *)&some_data, BUFSIZ,msg_to_receive, 0) == -1)
{
fprintf(stderr, "msgrcv failed with error: %d/n", errno);
exit(EXIT_FAILURE);
}
printf("You wrote: %s", some_data.some_text);
if (strncmp(some_data.some_text, "end", 3) == 0)
{
running = 0;
}
}
/*刪除消息隊列*/
if (msgctl(msgid, IPC_RMID, 0) == -1)
{
fprintf(stderr, "msgctl(IPC_RMID) failed/n");
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
③共享內存通信
share.h
#define TEXT_SZ 2048 //申請共享內存大小
struct shared_use_st
{
int written_by_you; //written_by_you為1時表示有數據寫入，為0時表示數據已經被消費者提走
char some_text[TEXT_SZ];
};
procer.c
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include "share.h"
int main()
{
int running = 1; //程序運行標志位
void *shared_memory = (void *)0;
struct shared_use_st *shared_stuff;
char buffer[BUFSIZ];
int shmid; //共享內存標識符
/*創建共享內存*/
shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666 | IPC_CREAT);
if (shmid == -1)
{
fprintf(stderr, "shmget failed/n");
exit(EXIT_FAILURE);
}
/*將共享內存連接到一個進程的地址空間中*/
shared_memory = shmat(shmid, (void *)0, 0);//指向共享內存第一個位元組的指針
if (shared_memory == (void *)-1)
{
fprintf(stderr, "shmat failed/n");
exit(EXIT_FAILURE);
}
printf("Memory attached at %X/n", (int)shared_memory);
shared_stuff = (struct shared_use_st *)shared_memory;
/*生產者寫入數據*/
while(running)
{
while(shared_stuff->written_by_you == 1)
{
sleep(1);
printf("waiting for client.../n");
}
printf("Enter some text: ");
fgets(buffer, BUFSIZ, stdin);
strncpy(shared_stuff->some_text, buffer, TEXT_SZ);
shared_stuff->written_by_you = 1;
if (strncmp(buffer, "end", 3) == 0)
{
running = 0;
}
}
/*該函數用來將共享內存從當前進程中分離,僅使得當前進程不再能使用該共享內存*/
if (shmdt(shared_memory) == -1)
{
fprintf(stderr, "shmdt failed/n");
exit(EXIT_FAILURE);
}
printf("procer exit./n");
exit(EXIT_SUCCESS);
}
customer.c
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include "share.h"
int main()
{
int running = 1;//程序運行標志位
void *shared_memory = (void *)0;
struct shared_use_st *shared_stuff;
int shmid; //共享內存標識符
srand((unsigned int)getpid());
/*創建共享內存*/
shmid = shmget((key_t)1234, sizeof(struct shared_use_st), 0666 | IPC_CREAT);
if (shmid == -1)
{
fprintf(stderr, "shmget failed/n");
exit(EXIT_FAILURE);
}
/*將共享內存連接到一個進程的地址空間中*/
shared_memory = shmat(shmid, (void *)0, 0);//指向共享內存第一個位元組的指針
if (shared_memory == (void *)-1)
{
fprintf(stderr, "shmat failed/n");
exit(EXIT_FAILURE);
}
printf("Memory attached at %X/n", (int)shared_memory);
shared_stuff = (struct shared_use_st *)shared_memory;
shared_stuff->written_by_you = 0;
/*消費者讀取數據*/
while(running)
{
if (shared_stuff->written_by_you)
{
printf("You wrote: %s", shared_stuff->some_text);
sleep( rand() % 4 );
shared_stuff->written_by_you = 0;
if (strncmp(shared_stuff->some_text, "end", 3) == 0)
{
running = 0;
}
}
}
/*該函數用來將共享內存從當前進程中分離,僅使得當前進程不再能使用該共享內存*/
if (shmdt(shared_memory) == -1)
{
fprintf(stderr, "shmdt failed/n");
exit(EXIT_FAILURE);
}
/*將共享內存刪除,所有進程均不能再訪問該共享內存*/
if (shmctl(shmid, IPC_RMID, 0) == -1)
{
fprintf(stderr, "shmctl(IPC_RMID) failed/n");
exit(EXIT_FAILURE);
}
exit(EXIT_SUCCESS);
}
摘自：http://blog.csdn.net/piaojun_pj/article/details/5943736
2. linux下，socket伺服器和客戶端TCP方式建立了連接，如何使它們之間相互發送消息
1.可能是在獲取客戶端的ip和埠時，處理出現問題，導致無法正確發送到客戶端。
2.客戶端是否使用固定的埠來接收伺服器信息，或伺服器是否正確發送到客戶端的相應的埠。
3.通過上面分析，最大可能是在處理埠出現問題，請重新檢查。
4.實在不行，最好使用拋出異常方法來捕獲錯誤消息，或是通過一步一步調試分析數據發送過程。