客戶端無法與服務器C連接（Socket編程）

Question

我有一個非常簡單的客戶端和服務器代碼：

客戶

int sockfd = 0; 
    int bytesReceived = 0; 
    char recvBuff[BUFSIZE]; 
    memset(recvBuff, '0', sizeof(recvBuff)); 
    struct sockaddr_in serv_addr; 
    printf("here i am\n"); 
    /* Create a socket first */ 
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0))< 0){ 
     printf("\n Error : Could not create socket \n"); 
     return 1; 
    } 
    fprintf(stderr, "connection stats\n"); 
    fprintf(stderr, "connecting to %d - %s \n",port,server); 
    /* Initialize sockaddr_in data structure */ 
    serv_addr.sin_family = AF_INET; 
    serv_addr.sin_port = htons(port); // port 
    serv_addr.sin_addr.s_addr = server; 
    printf(" attempting connection %s:%d\n", server, port); 
    /* Attempt a connection */ 
    int con = connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)); 
    printf("Error %d\n", con); 
    exit(-1); 

和服務器

int listenfd = 0; 
    int connfd = 0; 
    struct sockaddr_in serv_addr; 
    char sendBuff[BUFSIZE]; 
    int numrv; 

    listenfd = socket(AF_INET, SOCK_STREAM, 0); 

    printf("Socket retrieve success\n"); 

    memset(&serv_addr, '0', sizeof(serv_addr)); 
    memset(sendBuff, '0', sizeof(sendBuff)); 
    printf("here 2\n"); 
    serv_addr.sin_family = AF_INET; 
    printf("here 3\n"); 
    serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); 
    printf("here 4\n"); 
    serv_addr.sin_port = htons(port); 
    printf("here 5\n"); 
    int optval = 1; 
    printf(" opening port %d\n", port); 
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, 
       (const void *) &optval, sizeof(int)); 
    bind(listenfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)); 
    printf("binded\n"); 


    while (1) { 
     connfd = accept(listenfd, (struct sockaddr *) NULL, NULL); 
     printf("connfd %d", connfd); 


     close(connfd); 
     sleep(1); 


    } 

客戶端輸出：

here i am 
connecting to 8888 - localhost 
attempting connection localhost:8888 

服務器輸出

Socket retrieve success 
here 2 
here 3 
here 4 
here 5 
opening port 8888 
binded 

，等待像幾分鐘後..我注意以下事項： 客戶：

here i am 
connecting to 8888 - localhost 
attempting connection localhost:8888 
Error -1 

服務器：

Socket retrieve success 
here 2 
here 3 
here 4 
here 5 
opening port 8888 
binded 
connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd -1connfd 

其中由-1，我可以猜測連接失敗。 我不知道我失蹤了什麼？

Answer 1

在呼叫accept()之前，服務器錯過了在綁定套接字上調用listen()。

---

而且這個

serv_addr.sin_addr.s_addr = server; 

應該發出編譯器警告。你不能指定一個C-字符串（我認爲server是）到一個in_addr_t（serv_addr.sin_addr.s_addr是什麼）。

修復此做：

serv_addr.sin_addr.s_addr = inet_addr(server); 

或更好的錯誤檢查，這一點，像這樣：

{ 
    in_addr_t in_addr = inet_addr(server); 
    if (INADDR_NONE == in_addr) 
    { 
    perror("inet_addr() failed"); 
    abort(); /* or whatever error handling you choose. */ 
    } 

    serv_addr.sin_addr.s_addr = in_addr; 
}