C posix套接字，無法將數據從客戶端發送到服務器

Question

我想創建一個客戶端並將其連接到服務器。我知道客戶端進程在服務器之前開始運行，所以我在無限循環中進行連接，直到它接受爲止。然後我想輸入消息給客戶端併發送給服務器，服務器會在屏幕上打印它們。我刪除了代碼中的所有錯誤檢測，使其更短，我知道他們必須在那裏。我試圖這樣做，但服務器收不到任何東西，客戶端不能做第二次連接。

服務器

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; 
} 

客戶

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編譯你的代碼，但如果你已經設置了警示標誌（gcc中的-Wall）你會得到這個警告

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) { 

通過其代理，我變了，這個..

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

要..（注意額外的括號）

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

我沒有更多的額外的警告，並且服務器抓客戶的消息。

下面是在調試這個我跑的服務器（這基本上是有輕微的改變你的代碼）

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

另一個問題是，我們有我們每次做客戶端連接，如時間創建套接字：

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)); 
}