消息队列综合案例
消息队列实现回射客户/服务器
server进程接收时, 指定msgtyp为0, 从队首不断接收消息
server进程发送时, 将mtype指定为接收到的client进程的pid
client进程发送的时候, mtype指定为自己进程的pid
client进程接收时, 需要将msgtyp指定为自己进程的pid, 只接收消息类型为自己pid的消息;
// client/server进程接收/发送的数据结构
const int MSGMAX = 8192;
struct msgBuf
{long mtype; //保存客户进程的pid(需要将pid强制转换成为long)char mtext[MSGMAX]; //保存客户进程真实发送的数据
};//server.cpp
void echoServer(int msgid)
{struct msgBuf buf;int nrcv;while (true){bzero(&buf, sizeof(buf));if ((nrcv = msgrcv(msgid, &buf, sizeof(buf.mtext), 0, 0)) == -1)err_exit("msgrcv error");cout << "recv: " << buf.mtext;if (msgsnd(msgid, &buf, strlen(buf.mtext), 0) == -1)err_exit("msgsnd error");}
}int main()
{key_t key = ftok("/tmp/echoSeed", 0x1234);int msgid = msgget(key, IPC_CREAT|0666);if (msgid == -1)err_exit("msgget error");echoServer(msgid);
}//client.cpp
void echoServer(int msgid)
{struct msgBuf buf;int nrcv;while (true){bzero(&buf, sizeof(buf));if ((nrcv = msgrcv(msgid, &buf, sizeof(buf.mtext), 0, 0)) == -1)err_exit("msgrcv error");cout << "recv: " << buf.mtext;if (msgsnd(msgid, &buf, strlen(buf.mtext), 0) == -1)err_exit("msgsnd error");}
}int main()
{key_t key = ftok("/tmp/echoSeed", 0x1234);int msgid = msgget(key, IPC_CREAT|0666);if (msgid == -1)err_exit("msgget error");echoServer(msgid);
}附-ftok用法
#include <sys/types.h>
#include <sys/ipc.h>
key_t ftok(const char *pathname, int proj_id);描述信息:
The ftok() function uses the identity(象征) of the file named by the given pathname (which must refer
to an existing, accessible file[必须是一个已经存在,并且可访问的文件]) and the least significant(有效的) 8 bits[有效的最低8位] of proj_id (which must be nonzero) to generate a key_t type System V IPC key, suitable
for use with msgget(2), semget(2), or shmget(2). The resulting value is the same for all pathnames that name the same file, when the same value of proj_id
is used(如果文件名与proj_id的有效位全都相同的话, 则生成的key一定也是相同的). The value returned should be different when
the (simultaneously existing) files or the project IDs differ.
RETURN VALUE On success, the generated key_t value is returned. On failure -1 is returned,
with errno indicating the error as for the stat(2) system call.
