我正在处理一个服务器客户端项目，该项目允许服务器交换消息与客户单独交流。但是，我必须修改服务器，以便当服务器发送消息时，它会被发送到所有连接的客户端。
我知道这涉及到在线程之间共享变量，但我不知道该怎么做？
如有任何提示/指导，我们将不胜感激！
服务器代码：
#include<stdio.h>
#include<string.h> //strlen
#include<stdlib.h> //strlen
#include<sys/socket.h>
#include<arpa/inet.h> //inet_addr
#include<unistd.h> //write
#include<pthread.h> //for threading , link with lpthread
#define MAX 80
#define PORT 6543
#define SA struct sockaddr
// Function designed for chat between client and server.
void join( pthread_t *thread_id)
{
if(!pthread_join( *thread_id , NULL))
printf("thread %ld compltedn",*thread_id);
pthread_exit(0);//to exit the current thread
}
void func(int *sockfd)
{
char buff[MAX];
int n;
// infinite loop for chat
for (;;) {
bzero(buff, MAX);
// read the message from client and copy it in buffer
read(*sockfd, buff, sizeof(buff));
// print buffer which contains the client contents
printf("From client: %st To client : ", buff);
bzero(buff, MAX);
n = 0;
// copy server message in the buffer
while ((buff[n++] = getchar()) != 'n');
// and send that buffer to client
write(*sockfd, buff, sizeof(buff));
// if msg contains "Exit" then server exit and chat ended.
if (strncmp("exit", buff, 4) == 0) {
printf("Server Exit...n");
break;
}
}
}
// Driver function
int main()
{
int sockfd, connfd, len;
struct sockaddr_in servaddr, cli;
pthread_t thread_id,jointhread_id;
// socket create and verification
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd == -1) {
printf("socket creation failed...n");
exit(0);
}
else
printf("Socket successfully created..n");
bzero(&servaddr, sizeof(servaddr));
// assign IP, PORT
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = INADDR_ANY;
servaddr.sin_port = htons(PORT);
// Binding newly created socket to given IP and verification
if ((bind(sockfd, (SA*)&servaddr, sizeof(servaddr))) != 0) {
printf("socket bind failed...n");
exit(0);
}
else
printf("Socket successfully binded..n");
// Now server is ready to listen and verification
if ((listen(sockfd, 5)) != 0) {
printf("Listen failed...n");
exit(0);
}
else
printf("Server listening..n");
len = sizeof(cli);
// Accept the data packet from client and verification
while(connfd = accept(sockfd, (SA*)&cli, &len))
{
if (connfd < 0) {
printf("server acccept failed...n");
exit(0);
}
else
printf("server acccept the client..%d.n",connfd);
if( pthread_create( &thread_id , NULL , func , (void*) &connfd) < 0)
{
perror("could not create thread");
return 1;
}
if( pthread_create( &jointhread_id , NULL , join , (void*) &thread_id) < 0)
{
perror("could not create thread");
return 1;
}
}
// After chatting close the socket
close(sockfd);
}
不幸的是，出现了许多错误。。。
线程函数的原型错误
connfd的竞争条件，正如我在顶部评论中提到的(将connfd传递给func作为指针(。
执行getchar会破坏读取sockfd的消息数据
我在下面制作了一个版本来说明这一点。
但是，要使代码更接近您所声明的目的所需的内容，需要进行相当多的重构。下面还有第二个版本，说明了我对此的看法。
这里有一个带注释的版本，显示了错误和一些修复[主要是为了干净地编译它所花的时间]。
它用#if ORIG包装原始代码，用#if FIX包装新代码，每个地方都有一条关于它正在修复的错误的注释
#include <stdio.h>
#include <string.h> // strlen
#include <stdlib.h> // strlen
#include <sys/socket.h>
#include <arpa/inet.h> // inet_addr
#include <unistd.h> // write
#include <pthread.h> // for threading , link with lpthread
#define MAX 80
#define PORT 6543
#define SA struct sockaddr
#define ORIG 0
#define FIX 1
// Function designed for chat between client and server.
// NOTE/BUG -- the main thread has to join the thread
#if ORIG
void
join(pthread_t *thread_id)
{
if (!pthread_join(*thread_id, NULL))
printf("thread %ld compltedn", *thread_id);
// to exit the current thread
pthread_exit(0);
}
#endif
// NOTE/BUG: this is the _wrong_ signature for a thread function
#if ORIG
void
func(int *sockfd)
#else
void *
func(void *ptr)
#endif
{
#if FIX
int sockfd = (long) ptr;
#endif
char buff[MAX];
int n;
// infinite loop for chat
for (;;) {
bzero(buff, MAX);
// read the message from client and copy it in buffer
// NOTE/BUG: this has a race condition
// NOTE/BUG: we need the actual length
#if ORIG
read(*sockfd, buff, sizeof(buff));
#else
int rlen = read(sockfd, buff, sizeof(buff));
#endif
// print buffer which contains the client contents
printf("From client: %st To client : ", buff);
bzero(buff, MAX);
// copy server message in the buffer
// NOTE/BUG: this is destroying the data that was
#if ORIG
n = 0;
while ((buff[n++] = getchar()) != 'n');
#endif
// and send that buffer to client
#if ORIG
write(*sockfd, buff, sizeof(buff));
#else
write(sockfd, buff, rlen);
#endif
// if msg contains "Exit" then server exit and chat ended.
if (strncmp("exit", buff, 4) == 0) {
printf("Server Exit...n");
break;
}
}
// NOTE/BUG: we must return the error code
#if FIX
return (void *) 0;
#endif
}
// Driver function
int
main()
{
int sockfd, connfd, len;
struct sockaddr_in servaddr, cli;
pthread_t thread_id, jointhread_id;
// socket create and verification
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd == -1) {
printf("socket creation failed...n");
exit(0);
}
else
printf("Socket successfully created..n");
// assign IP, PORT
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = INADDR_ANY;
servaddr.sin_port = htons(PORT);
// Binding newly created socket to given IP and verification
if ((bind(sockfd, (SA *) & servaddr, sizeof(servaddr))) != 0) {
printf("socket bind failed...n");
exit(0);
}
else
printf("Socket successfully binded..n");
// Now server is ready to listen and verification
if ((listen(sockfd, 5)) != 0) {
printf("Listen failed...n");
exit(0);
}
else
printf("Server listening..n");
// Accept the data packet from client and verification
len = sizeof(cli);
// NOTE/BUG: connfd can be zero for a valid connection
#if ORIG
while (connfd = accept(sockfd, (SA *) &cli, &len)) {
#else
while (1) {
connfd = accept(sockfd, (SA *) &cli, &len);
#endif
if (connfd < 0) {
printf("server acccept failed...n");
exit(0);
}
else
printf("server acccept the client..%d.n", connfd);
#if ORIG
if (pthread_create(&thread_id, NULL, func, (void *) &connfd) < 0) {
perror("could not create thread");
return 1;
}
#else
if (pthread_create(&thread_id, NULL, func, (void *) ((long) connfd)) < 0) {
perror("could not create thread");
return 1;
}
#endif
// NOTE/BUG -- creating a separate thread just to join the above thread does
// not help
#if ORIG
if (pthread_create(&jointhread_id, NULL, join, (void *) &thread_id) < 0) {
perror("could not create thread");
return 1;
}
#endif
}
// After chatting close the socket
close(sockfd);
return 0;
}
这里有一个重构版本，它实现了您想要的多客户端消息回显。
它使用每个线程的任务块来控制事情。每个客户端在接收到消息时，都会将其发送给所有其他客户端。
它还使用互斥执行一些线程间锁定。
让一个给定的客户端线程对其他客户端执行所有的回显只是一种方法。还有其他(例如，所有客户端线程都将消息排队到主/主线程，它执行回显(
这要近得多，但在func中要接收/发送客户端消息还有更多的工作要做。
无论如何，这是代码：
#include <stdio.h>
#include <string.h> // strlen
#include <stdlib.h> // strlen
#include <sys/socket.h>
#include <arpa/inet.h> // inet_addr
#include <unistd.h> // write
#include <pthread.h> // for threading , link with lpthread
#define MAX 80
#define PORT 6543
#define SA struct sockaddr
#define ORIG 0
#define FIX 1
enum {
TSKSTATE_IDLE, // task slot free/available
TSKSTATE_PENDING, // task is being created
TSKSTATE_RUNNING, // task is alive and running
TSKSTATE_DONE // task has completed (but not reaped)
};
typedef struct tsk tsk_t;
struct tsk {
tsk_t *tsk_next; // chain pointer
pthread_t tsk_tid; // thread id
long tsk_xid; // sequential task id
int tsk_sockfd; // client socket descriptor
int tsk_state; // current task state
pthread_mutex_t tsk_mutex; // per-thread mutex
void *tsk_rtn; // thread's return value
};
// NOTE: using an array obviates the need for a master lock if we used a
// linked list here instead -- by passing TSKMAX to listen below [in main],
// we guarantee that main can always find a free task slot when it needs one
#define TSKMAX 5
tsk_t tsklist[TSKMAX]; // active task list
#define TSKFORALL(_tsk)
_tsk = &tsklist[0]; _tsk < &tsklist[TSKMAX]; ++_tsk
long tskxid; // sequential task id
__thread tsk_t *tskcur; // current thread's tsk block
pthread_mutex_t master_lock = PTHREAD_MUTEX_INITIALIZER;
// lockall -- lock all threads
void
lockall(void)
{
pthread_mutex_lock(&master_lock);
}
// unlockall -- lock all threads
void
unlockall(void)
{
pthread_mutex_unlock(&master_lock);
}
// tsklock -- lock single thread
void
tsklock(tsk_t *tsk)
{
pthread_mutex_lock(&tsk->tsk_mutex);
}
// tskunlock -- unlock single thread
void
tskunlock(tsk_t *tsk)
{
pthread_mutex_unlock(&tsk->tsk_mutex);
}
// tskreapall -- release all completed threads
void
tskreapall(void)
{
tsk_t *tsk;
lockall();
for (TSKFORALL(tsk)) {
tsklock(tsk);
if (tsk->tsk_state == TSKSTATE_DONE) {
pthread_join(tsk->tsk_tid,&tsk->tsk_rtn);
tsk->tsk_state = TSKSTATE_IDLE;
}
tskunlock(tsk);
}
}
// tsksendall -- send message to all other clients
void
tsksendall(char *msg,int len)
{
tsk_t *tsk;
lockall();
for (TSKFORALL(tsk)) {
if (tsk == tskcur)
continue;
tsklock(tsk);
if (tsk->tsk_state == TSKSTATE_RUNNING)
write(tsk->tsk_sockfd,msg,len);
tskunlock(tsk);
}
}
void *
func(void *ptr)
{
tskcur = ptr;
char buff[MAX];
#if ORIG
int n;
#endif
tsklock(tskcur);
tskcur->tsk_state = TSKSTATE_RUNNING;
tskunlock(tskcur);
// infinite loop for chat
// NOTE: this loop still needs work ...
for (;;) {
bzero(buff, MAX);
// read the message from client and copy it in buffer
int rlen = read(tskcur->tsk_sockfd, buff, sizeof(buff));
// print buffer which contains the client contents
printf("From client: %st To client : ", buff);
bzero(buff, MAX);
// copy server message in the buffer
// NOTE/BUG: this is destroying the data that was
#if ORIG
n = 0;
while ((buff[n++] = getchar()) != 'n');
#endif
// and send that buffer to client
write(tskcur->tsk_sockfd, buff, rlen);
// if msg contains "Exit" then server exit and chat ended.
if (strncmp("exit", buff, 4) == 0) {
printf("Server Exit...n");
break;
}
// echo message to all other clients
tsksendall(buff,rlen);
}
tsklock(tskcur);
tskcur->tsk_state = TSKSTATE_DONE;
close(tskcur->tsk_sockfd);
tskcur->tsk_sockfd = -1;
tskunlock(tskcur);
return (void *) 0;
}
// Driver function
int
main(void)
{
int sockfd, connfd;
socklen_t len;
struct sockaddr_in servaddr, cli;
int state;
tsk_t *tsktry;
tsk_t *tsknew;
// socket create and verification
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd == -1) {
printf("socket creation failed...n");
exit(0);
}
else
printf("Socket successfully created..n");
// assign IP, PORT
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = INADDR_ANY;
servaddr.sin_port = htons(PORT);
// Binding newly created socket to given IP and verification
if ((bind(sockfd, (SA *) & servaddr, sizeof(servaddr))) != 0) {
printf("socket bind failed...n");
exit(0);
}
else
printf("Socket successfully binded..n");
// Now server is ready to listen and verification
if ((listen(sockfd, TSKMAX)) != 0) {
printf("Listen failed...n");
exit(0);
}
else
printf("Server listening..n");
// Accept the data packet from client and verification
len = sizeof(cli);
for (TSKFORALL(tsktry)) {
pthread_mutex_init(&tsktry->tsk_mutex,NULL);
tsktry->tsk_state = TSKSTATE_IDLE;
}
while (1) {
connfd = accept(sockfd, (SA *) &cli, &len);
if (connfd < 0) {
printf("server acccept failed...n");
exit(0);
}
else
printf("server acccept the client..%d.n", connfd);
// reap all completed threads
tskreapall();
// find an idle slot
tsknew = NULL;
for (TSKFORALL(tsktry)) {
tsklock(tsktry);
state = tsktry->tsk_state;
if (state == TSKSTATE_IDLE) {
tsknew = tsktry;
tsknew->tsk_state = TSKSTATE_PENDING;
}
tskunlock(tsktry);
if (tsknew != NULL)
break;
}
tsknew->tsk_xid = ++tskxid;
tsknew->tsk_sockfd = connfd;
if (pthread_create(&tsknew->tsk_tid, NULL, func, tsknew) < 0) {
perror("could not create thread");
return 1;
}
}
// After chatting close the socket
close(sockfd);
return 0;
}