C 套接字编程 - 从服务器写入(而不是客户端)写入服务器

标签 c sockets tcp server client

我正在开发一个 TCP 客户端服务器程序，它应该支持使用线程的多个客户端。

套接字创建、连接、绑定(bind)和接受按预期工作，因为我在运行代码时没有收到任何错误。
但是，每当我尝试从服务器读取()时，代码都会进入无限循环，并且没有任何 react 。

我先尝试从服务器写入，然后将写入结果写入服务器的终端。

客户端代码:

#include <stdlib.h>
#include <stdio.h>
#include <stdio.h>
#include <unistd.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <dirent.h>

#define FILE_ADDR   "/dev/urandom"

int main(int argc, char *argv[]) {

    //Get command line arguments
    unsigned int port = atoi(argv[2]);
    int length = atoi(argv[3]); //Number of bytes to read
    char* buffer = malloc(length * sizeof(char)); //Buffer to hold data read from file
    char* recvBuf = malloc(10 * sizeof(char)); // Buffer to hold response from server

    struct addrinfo hints, *servinfo, *p;
    struct sockaddr_in serv_addr;
    int sockfd = -1;
    //int rv;
    //char ip[100];

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    int rv = getaddrinfo(argv[1], argv[2], &hints, &servinfo);
    if (rv != 0) {
        perror("getaddrinfo error\n");
        exit(1);
    }
    for (p = servinfo; p != NULL; p = p->ai_next) {
        //Initialize socket
        sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if (sockfd < 0)
            continue;
        //Initialize connection
        rv = connect(sockfd, p->ai_addr, (socklen_t) p->ai_addrlen);
        if (rv == 0)
            break;
        close(sockfd);
        sockfd = -1;
    }
    //   inet_aton(ip, &h.sin_addr);
    freeaddrinfo(servinfo);

    //Open file for reading
    FILE *fp;
    fp = fopen(FILE_ADDR, "r");
    if (fp == NULL) {
        perror("Error in file open\n");
    }
    printf("file opened\n");
    size_t numOfbytesRead = fread(buffer, sizeof(char), length, fp);
    if (numOfbytesRead != length) {
        perror("Error reading from file\n");
    }
    printf("Buffer is %s\n", buffer);

    char* ptr;
    unsigned int N = strtoul(argv[3],&ptr,10);
    int convertedNum = htonl(N);

    if (write(sockfd, &convertedNum, sizeof(unsigned int)) < 0) {   //Send number of bytes
        perror("error writing to socket");
    }
    if (write(sockfd, buffer, sizeof(buffer) < 0)) {//Send bytes read from file
        perror("error writing to socket");

    }

    printf("send is done \n");

    int bytes_read = read(sockfd, recvBuf, sizeof(recvBuf)); //Recieve response from server
    if (bytes_read <= 0) {
        perror("Error in recieving result from server\n");
    }

    unsigned int C = 0;
    sprintf(recvBuf[0], "%d", C);

    fclose(fp);
    printf("# of printable characters: %u\n", C);
    exit(0);
    free(buffer);
    free(recvBuf);

}

服务器代码:
#include <stdlib.h>
#include <stdio.h>
#include <stdio.h>
#include <unistd.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <dirent.h>
#include <pthread.h>
#include <signal.h>

static volatile int keepRunning = 1;
int pcc_total[159];

void intHandler(int dummy) {
    keepRunning = 0;
}

void *compute(void *socket_desc) {
    int count = 0;
    int sock = *(int*) socket_desc;
    printf("now will allocate N \n");
    int n=0;
    if (write(sock, "hi", 2) < 0) { //Send number of bytes
        perror("error writing to socket\n");
    }
    if (read(sock, &n, sizeof(unsigned int)) < 0) {
        perror("Error reading from socket\n");
        exit(1);
    }
    int N = ntohl(n);
    printf("len is %d\n", N);
    char* data = calloc(N, sizeof(char));
    int len = read(sock, data, N);
    printf("data is %s\n", data);
    if (len < 0) {
        perror("Error reading from socket\n");
        exit(1);
    }
    for (int i = 0; i < len; i++) {
        int tmp = 0;
        sprintf(data[i], "%d", tmp);
        if (tmp >= 32 & tmp <= 126) {
            count++;

            __sync_fetch_and_add(&pcc_total[tmp], 1);
        }
    }
    char scount[100];
    atoi(count);
    write(sock, count, strlen(scount));
    free(data);
    pthread_exit(NULL);
    close(sock);
    exit(0);
}

int main(int argc, char *argv[]) {

    unsigned int port = atoi(argv[1]);
    signal(SIGINT, intHandler);

    int socket_desc, client_sock, c, *new_sock;
    struct sockaddr_in server, client;
    c = sizeof(struct sockaddr_in);

    socket_desc = socket( AF_INET, SOCK_STREAM, 0);
    if (socket_desc == -1) {
        perror("Could not create socket");
        exit(1);
    }
    printf("socket created\n");
    memset(&server, 0, c);

    server.sin_family = AF_INET;
    server.sin_addr.s_addr = htonl(INADDR_ANY);
    server.sin_port = htons(port);

    if (0 != bind(socket_desc, (struct sockaddr*) &server, sizeof(server))) {
        perror("\n Error : Bind Failed \n");
        exit(1);
    }
    printf("bind created\n");
    if (0 != listen(socket_desc, 10)) {
        perror("\n Error : Listen Failed \n");
        exit(1);
    }
    printf("listen created\n");
    while (keepRunning) {
        client_sock = accept(socket_desc, (struct sockaddr *) &client,
                (socklen_t*) &c);
        if (client_sock < 0) {
            perror("\n Error : Accept Failed\n");
            exit(1);
        }
        printf("accept created\n");
        pthread_t tid;
        new_sock = malloc(100*sizeof(int));
        *new_sock = client_sock;
        if ((pthread_create(&tid, NULL, compute, (void*) new_sock)) < 0) {
            perror("could not create thread\n");
            exit(1);
        }
        printf("thread created\n");
        // close socket
        close(client_sock);
        free(new_sock);
        pthread_join(tid, NULL);
    }

    exit(0);

}

我使用以下命令运行代码:

gcc -std=c99 -O3 -Wall -o pcc_server pcc_server.c -pthread

gcc -std=gnu99 -O3 -Wall -o pcc_client pcc_client.c

最佳答案

您的代码存在许多问题。
在客户端:

  • 打电话时fread() ，您需要使用 "rb"而不是 "r" .
  • 打电话时printf()要输出实际读取的文件数据，您不是空终止 buffer ，或传递其 length至 printf() .你需要这样做。
  • 您正在分配 htonl() 的返回值到 int而不是 unsigned int .
  • 打电话时write()发送 buffer , 您正在使用 sizeof(buffer)什么时候应该使用 length或 N相反(以及为什么要使用两个单独的变量来保存相同的命令行参数值？)。 buffer是指向用 malloc() 分配的内存的指针, 所以 sizeof(buffer)与 sizeof(void*) 相同，这不是您想要的。此外，您甚至没有调用 write()正确，因为您的括号都是错误的(在发送 write() 时，它们在之前的 convertedNum 调用中是正确的)。
  • 同样，在调用 read() 时阅读 recvBuf , 您正在使用 sizeof(recvBuf)什么时候应该使用 10相反，西涅recvBuf也是指向 malloc 的指针ed 内存。
  • 您没有阅读 "hi"服务器在连接时发送给客户端的问候语，因此您将这些字节与下一条消息的以下大小值的字节混在一起，从而以损坏的 C 结束。值(value)。

    • 在服务器端:
  • 您的 compute线程例程发送 "hi"对客户端的问候，但它不使用任何类型的分隔符，例如在问候前加上其长度，或用换行符或空字符或其他唯一字符终止它，以将其与任何后续数据分开。您应该始终以某种方式分隔您的消息。
  • 您正在关闭 accept ed 套接字并释放 malloc编辑 new_sock一旦您创建了一个工作线程来处理该客户端。您正在从线程众所周知的背后撕掉内存。线程需要是关闭套接字并在使用完毕后释放内存的线程，而不是 accept环形。
    该线程确实尝试关闭套接字(但不释放内存)，但在调用 pthread_exit() 之后首先，这是错误的。 pthread_exit()终止调用线程，所以它需要是线程调用的最后一件事(不要调用 exit() !)。事实上，甚至不要打电话pthread_exit()完全直接，只是return来自 compute() ，然后 pthreads 库将调用 pthread_exit()为你，随便传递 void*您选择的值 return .
  • 您的 accept循环不应调用 pthread_join()根本。它阻塞调用线程，直到指定的线程终止。这违背了使用线程处理客户端的全部目的，并阻止您的服务器一次接受 1 个以上的客户端。如果您打算使用 pthread_join()总而言之，它应该在 accept 之后循环已结束，因此您可以在退出应用程序之前等待任何可能仍在运行的工作线程。但这也意味着跟踪 pthread_t pthread_create() 的值返回，这是更多的工作。

    • 话虽如此，请尝试使用以下代码:
    客户端代码:
    #include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <dirent.h>

#define FILE_ADDR   "/dev/urandom"

char* readMsg(int sockfd, size_t *msgSize)
{
    *msgSize = 0;

    unsigned int length = 0;
    int bytes_read = read(sockfd, &length, sizeof(length)); //Receive number of bytes
    if (bytes_read <= 0) {
        perror("Error in receiving message from server\n");
        return NULL;
    }
    length = ntohl(length);

    char *buffer = malloc(length+1);
    if (!buffer) {
        perror("Error in allocating memory to receive message from server\n");
        return NULL;
    }

    char *pbuf = buffer;
    unsigned int buflen = length;
    while (buflen > 0) {
        bytes_read = read(sockfd, pbuf, buflen); // Receive bytes
        if (bytes_read <= 0) {
            perror("Error in receiving message from server\n");
            free(buffer);
            return NULL;
        }
        pbuf += bytes_read;
        buflen -= bytes_read;
    }

    *msgSize = length;
    return buffer;
}

int sendMsg(int sockfd, char *msg, size_t msgSize)
{
    unsigned int convertedNum = htonl(msgSize);
    if (write(sockfd, &convertedNum, sizeof(convertedNum)) < 0) { //Send number of bytes
        perror("error writing to socket");
        return -1;
    }

    if (write(sockfd, msg, msgSize) < 0) { //Send bytes
        perror("error writing to socket");
        return -1;
    }

    return 0;
}

int main(int argc, char *argv[]) {

    char* ptr;

    //Get command line arguments
    unsigned int port = atoi(argv[2]);
    unsigned int length = strtoul(argv[3], &ptr, 10); //Number of bytes to read
    char* buffer = malloc(length); //Buffer to hold data read from file

    struct addrinfo hints, *servinfo, *p;
    struct sockaddr_in serv_addr;
    int sockfd = -1;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;

    int rv = getaddrinfo(argv[1], argv[2], &hints, &servinfo);
    if (rv != 0) {
        perror("getaddrinfo error\n");
        return 1;
    }
    for (p = servinfo; p != NULL; p = p->ai_next) {
        //Initialize socket
        sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol);
        if (sockfd < 0)
            continue;
        //Initialize connection
        rv = connect(sockfd, p->ai_addr, (socklen_t) p->ai_addrlen);
        if (rv == 0)
            break;
        close(sockfd);
        sockfd = -1;
    }
    freeaddrinfo(servinfo);

    if (sockfd == -1) {
        perror("socket create/connect error\n");
        return 1;
    }

    size_t msgSize;
    char *msg = readMsg(sockfd, &msgSize);
    if (!msg) {
        close(sockfd);
        return 1;
    }
    printf("%.*s\n", (int)msgSize, msg);
    free(msg);

    //Open file for reading
    FILE *fp = fopen(FILE_ADDR, "rb");
    if (fp == NULL) {
        perror("Error in file open\n");
        close(sockfd);
        return 1;
    }
    printf("file opened\n");

    if (fread(buffer, 1, length, fp) != length) {
        perror("Error reading from file\n");
        fclose(fp);
        close(sockfd);
        return 1;
    }
    fclose(fp);
    printf("Buffer is %.*s\n", (int)length, buffer);

    if (sendMsg(sockfd, buffer, length) != 0) {
        free(buffer);
        close(sockfd);
        return 1;
    }
    free(buffer);
    printf("send is done \n");

    msg = readMsg(sockfd, &msgSize); // response from server
    if (!msg) {
        close(sockfd);
        return 1;
    }
    printf("# of printable characters: %.*s\n", (int)msgSize, msg);
    free(msg);

    return 0;
}
    服务器代码:
    #include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <dirent.h>
#include <pthread.h>
#include <signal.h>

static volatile int keepRunning = 1;
int pcc_total[159];

void intHandler(int dummy) {
    keepRunning = 0;
}

char* readMsg(int sockfd, size_t *msgSize)
{
    *msgSize = 0;

    unsigned int length = 0;
    int bytes_read = read(sockfd, &length, sizeof(length)); //Receive number of bytes
    if (bytes_read <= 0) {
        perror("Error in receiving message from server\n");
        return NULL;
    }
    length = ntohl(length);

    char *buffer = malloc(length+1);
    if (!buffer) {
        perror("Error in allocating memory to receive message from server\n");
        return NULL;
    }

    char *pbuf = buffer;
    unsigned int buflen = length;
    while (buflen > 0) {
        bytes_read = read(sockfd, pbuf, buflen); // Receive bytes
        if (bytes_read <= 0) {
            perror("Error in receiving message from server\n");
            free(buffer);
            return NULL;
        }
        pbuf += bytes_read;
        buflen -= bytes_read;
    }

    *msgSize = length;
    return buffer;
}

int sendMsg(int sockfd, char *msg, size_t msgSize)
{
    unsigned int convertedNum = htonl(msgSize);
    if (write(sockfd, &convertedNum, sizeof(convertedNum)) < 0) { //Send number of bytes
        perror("error writing to socket");
        return -1;
    }

    if (write(sockfd, msg, msgSize) < 0) { //Send bytes
        perror("error writing to socket");
        return -1;
    }

    return 0;
}

void *compute(void *socket_desc) {
    int sock = * (int*) socket_desc;
    free(socket_desc);

    if (sendMsg(sock, "hi", 2) != 0) {
        perror("error writing to socket\n");
        close(sock);
        return NULL;
    }

    size_t length = 0;
    char *data = readMsg(sock, &length);
    if (!msg) {
        close(sock);
        return NULL;
    }
    printf("len is %d\n", (int)length);
    printf("data is %.*s\n", (int)length, data);

    int count = 0;
    for (size_t i = 0; i < length; i++) {
        // ...
    }
    free(data);

    char scount[20];
    sprintf(scount, "%d", count);
    sendMsg(sock, scount, strlen(scount));

    close(sock);
    return NULL;
}

int main(int argc, char *argv[]) {

    unsigned int port = atoi(argv[1]);
    signal(SIGINT, intHandler);

    int socket_desc, client_sock, c, *new_sock;
    struct sockaddr_in server, client;

    socket_desc = socket( AF_INET, SOCK_STREAM, 0);
    if (socket_desc == -1) {
        perror("Could not create server socket");
        return 1;
    }
    printf("server socket created\n");

    memset(&server, 0, c);
    server.sin_family = AF_INET;
    server.sin_addr.s_addr = htonl(INADDR_ANY);
    server.sin_port = htons(port);

    if (bind(socket_desc, (struct sockaddr*) &server, sizeof(server)) < 0) {
        perror("\n Error : Bind Failed \n");
        close(socket_desc);
        return 1;
    }
    printf("bind created\n");

    if (listen(socket_desc, 10) < 0) {
        perror("\n Error : Listen Failed \n");
        close(socket_desc);
        return 1;
    }
    printf("listening\n");

    while (keepRunning) {
        c = sizeof(client);
        client_sock = accept(socket_desc, (struct sockaddr *) &client,
                            (socklen_t*) &c);
        if (client_sock < 0) {
            perror("\n Error : Accept Failed\n");
            continue;
        }
        printf("client accepted\n");

        new_sock = malloc(sizeof(int));
        if (!new_sock) {
            perror("\n Error : Malloc Failed\n");
            close(client_sock);
            continue;
        }
        *new_sock = client_sock;

        pthread_t tid;
        if (pthread_create(&tid, NULL, &compute, new_sock) != 0) {
            perror("\n Error : Thread Create Failed\n");
            free(new_sock);
            close(client_sock);
            continue;
        }
        printf("thread created\n");
    }

    close(socket_desc);
    return 0;
}

    关于C 套接字编程 - 从服务器写入(而不是客户端)写入服务器，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48389076/

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