修复：C++ server/client 程序："Connection refused"

Question

我正在编写一个简单的程序来将文件从服务器传输到客户端（目前都在同一台计算机上）。使用"telnet 127.0.0.1 [port]"，我可以成功从服务器获取文件，但是当我运行客户端时，服务器拒绝连接。我怀疑客户端试图连接到错误的地址，但我不确定。如果有帮助，我还添加了一些 GDB 测试输出。

服务器：“./server 0 4100 大文件 100 0.01”

int main(int argc, char* argv[]) 
{
    int sockfd;
    if(!(sockfd = socket(AF_INET, SOCK_STREAM, 0))) {
        error("Failed to create socket");
    }

    struct sockaddr_in serv_addr, cl_addr;
    bzero((void*) &serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    serv_addr.sin_port = htons(atoi(argv[2]));
    if(bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
        error("Failed to bind");
    }
    listen(sockfd, 10);

    int fd = open(argv[3], O_RDONLY);
    int bufsize = atoi(argv[4]);
    int packet_period = atoi(argv[5]);
    size_t cl_addr_len = sizeof(cl_addr);
    char *buf = new char[bufsize];
    while(true) {
        int sd;
        cout << "waiting for client..." << endl;
        if(!(sd = accept(sockfd, (struct sockaddr *) &cl_addr, (socklen_t*) &cl_addr_len))) {
            error("Failed to acccept");
        }
        cout << "Accepted client connection" << endl;
        lseek(fd, 0, SEEK_SET);
        while(int n = read(fd, buf, bufsize)) {
            cout << "Transferring " << buf << endl;
            usleep(100000);
            write(sd, buf, n);
        }
    }
}

客户端：“./client 0 127.0.0.1 4100 大文件统计”

int main(int argc, char *argv[])
{
    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd < 0) {
        error("Failed to open socket");
    }

    struct sockaddr_in serv_addr;
    bzero((char *) &serv_addr, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(argv[2]);
    serv_addr.sin_port = htons(atoi(argv[3])); // I tried both htons and htonl
    if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0) {
        error("Failed to connect");
    }

    int n;
    char buf[256];
    int fd = open(argv[4], O_RDONLY);
    while((n = read(sockfd, buf, 256)) > 0) {
        printf("Received: %s\n", buf);
        write(fd, buf, n);
    }

    close(fd);
    close(sockfd);
    return 0;
}

GDB 输出：

(gdb) r
Starting program: [...]/client 0 127.0.0.1 4100 bigfile stats

Breakpoint 1, main (argc=6, argv=0x7fffffffde68) at client.cpp:31
31      if (connect(sockfd,(struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {

(gdb) p serv_addr
 = {sin_family = 2, sin_port = 0, sin_addr = {s_addr = 16777343}, 
  sin_zero = "[=14=]0[=14=]0[=14=]0[=14=]0[=14=]0[=14=]0[=14=]0"}

Answer 1

{sin_family = 2, sin_port = 0, sin_addr = {s_addr = 16777343}, sin_zero = "[=10=]0[=10=]0[=10=]0[=10=]0[=10=]0[=10=]0[=10=]0"}

所以 sin_port 是错误的：它不应该为零。设置它的代码是：

serv_addr.sin_port = htonl(atoi(argv[3]));

问题就在这里。应该是

serv_addr.sin_port = htons(atoi(argv[3]));

不是今天的问题而是

printf("Received: %s\n", buf);

应该是

printf("Received: %.*s\n", n, buf);

修复：C++ server/client 程序："Connection refused"

FIXED: C++ server/client program: "Connection refused"

c

c++

sockets

gdb

client-server