C posix套接字，无法将数据从客户端发送到服务器

Question

我想创建一个客户端并将其连接到服务器。我知道客户端进程在服务器之前开始运行，所以我在无限循环中进行连接，直到它接受为止。然后我想输入消息给客户端并发送给服务器，服务器会在屏幕上打印它们。我删除了代码中的所有错误检测，使其更短，我知道他们必须在那里。我试图这样做，但服务器收不到任何东西，客户端不能做第二次连接。

服务器

int main(int argc, char *argv[]) 
{ 
    int sockfd, newsockfd; 
    socklen_t clilen; 
    char buffer[256]; 
    struct sockaddr_in serv_addr, cli_addr; 
    sockfd = socket(AF_INET, SOCK_STREAM, 0); 
    serv_addr.sin_family = AF_INET; 
    serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1"); 
    serv_addr.sin_port = htons(5000); 
    bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)); 
    listen(sockfd, 5); 
    clilen = sizeof(cli_addr); 
    while (newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr,&clilen) >= 0) 
    { 
     read(newsockfd, buffer, 255); 
     close(newsockfd); 
    } 
    close(sockfd); 
    return 0; 
} 

客户

int main(int argc, char *argv[]) 
    { 
    int sockfd; 
    struct sockaddr_in serv_addr; 

    char buffer[256]; 
    sockfd = socket(AF_INET, SOCK_STREAM, 0); 
    serv_addr.sin_family = AF_INET; 
    serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1"); 
    serv_addr.sin_port = htons(5000); 
    while (1) { 
     while ((connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)) { 
      printf("trying to connect\n"); 
      sleep(1); 
     } 
     printf("connected\nplease, enter a message\n"); 
     scanf("%s", buffer); 
     write(sockfd, buffer, strlen(buffer)); 
    } 
    close(sockfd); 
    return 0; 
} 

Answer 1

我不只是知道你是如何编译你的代码，但如果你已经设置了警示标志（gcc中的-Wall）你会得到这个警告

server.c: In function ‘main’: 
server.c:33:44: warning: suggest parentheses around assignment used as truth value [-Wparentheses] 
if (newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr,&clilen) >= 0) { 

通过其代理，我变了，这个..

if (newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr,&clilen) >= 0) { 

要..（注意额外的括号）

if ((newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr,&clilen)) >= 0) { 

我没有更多的额外的警告，并且服务器抓客户的消息。

下面是在调试这个我跑的服务器（这基本上是有轻微的改变你的代码）

int sockfd, newsockfd; 
socklen_t clilen; 
char buffer[256]; 
int nbytes = 0; 
struct sockaddr_in serv_addr, cli_addr; 
sockfd = socket(AF_INET, SOCK_STREAM, 0); 
serv_addr.sin_family = AF_INET; 
//serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1"); 
serv_addr.sin_addr.s_addr = INADDR_ANY; 
serv_addr.sin_port = htons(5007); 
bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)); 


if (listen(sockfd, 5) <0) { } 

clilen = sizeof(cli_addr); 
if ((newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr,&clilen)) >= 0) { 

    while ((nbytes = read(newsockfd, buffer, sizeof(buffer)))<0) { 
     sleep(1); 
    } 

    printf("client sent: %s", buffer); 
} 
close(newsockfd); 
close(sockfd); 
return 0; 

Answer 2

另一个问题是，我们有我们每次做客户端连接，如时间创建套接字：

while (1) { 
    sockfd = socket(AF_INET, SOCK_STREAM, 0); 
    while ((connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)) { 
     printf("trying to connect\n"); 
     sleep(1); 
    } 
    printf("connected\nplease, enter a message\n"); 
    scanf("%s", buffer); 
    write(sockfd, buffer, strlen(buffer)); 
}