Server only receiving null string from client? : <p>So I have a basic client/server c++ program. Right now, when the client connects to the server I want the server sends a "Hello, world" message and the client to respond "Hello, server" just to make sure I am sending and relieving messages correctly. </p>

<p>When I run, the client receives the message from the server, but the server only receives a null string from the client. </p>

<p>Here is the code for the client</p>

<pre><code>int main(int argc, char *argv[]) {
int sockfd, numbytes;  
char buf[MAXDATASIZE];
struct addrinfo hints, *servinfo, *p;
int rv;
char s[INET6_ADDRSTRLEN];

if (argc != 2) {
    fprintf(stderr,"usage: client hostname\n");
    exit(1);
}

memset(&amp;hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;

if ((rv = getaddrinfo(argv[1], PORT, &amp;hints, &amp;servinfo)) != 0) {
    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
    return 1;
}

// loop through all the results and connect to the first we can
for(p = servinfo; p != NULL; p = p-&gt;ai_next) {
    if ((sockfd = socket(p-&gt;ai_family, p-&gt;ai_socktype,
            p-&gt;ai_protocol)) == -1) {
        perror("client: socket");
        continue;
    }

    if (connect(sockfd, p-&gt;ai_addr, p-&gt;ai_addrlen) == -1) {
        close(sockfd);
        perror("client: connect");
        continue;
    }

    break;
}

if (p == NULL) {
    fprintf(stderr, "client: failed to connect\n");
    return 2;
}

inet_ntop(p-&gt;ai_family, get_in_addr((struct sockaddr *)p-&gt;ai_addr),
        s, sizeof s);
printf("client: connecting to %s\n", s);

freeaddrinfo(servinfo); // all done with this structure

if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) {
    perror("recv");
    exit(1);
}

if (send(sockfd, "Hello, client!", 13, 0) == -1) {
            perror("send");
}

buf[numbytes] = '\0';

printf("client: received '%s'\n",buf);

close(sockfd);

return 0;
}
</code></pre>

<p>and Here's the code for the server</p>

<pre><code>int main(void)
{
    int sockfd, new_fd, numbytes;  // listen on sock_fd, new connection on    new_fd
char buf[MAXDATASIZE];
struct addrinfo hints, *servinfo, *p;
struct sockaddr_storage their_addr; // connector's address information
socklen_t sin_size;
struct sigaction sa;
int yes=1;
char s[INET6_ADDRSTRLEN];
int rv;

memset(&amp;hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE; // use my IP

if ((rv = getaddrinfo(NULL, PORT, &amp;hints, &amp;servinfo)) != 0) {
    fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
    return 1;
}

// loop through all the results and bind to the first we can
for(p = servinfo; p != NULL; p = p-&gt;ai_next) {
    if ((sockfd = socket(p-&gt;ai_family, p-&gt;ai_socktype,
            p-&gt;ai_protocol)) == -1) {
        perror("server: socket");
        continue;
    }

    if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &amp;yes,
            sizeof(int)) == -1) {
        perror("setsockopt");
        exit(1);
    }

    if (bind(sockfd, p-&gt;ai_addr, p-&gt;ai_addrlen) == -1) {
        close(sockfd);
        perror("server: bind");
        continue;
    }

    break;
}

freeaddrinfo(servinfo); // all done with this structure

if (p == NULL)  {
    fprintf(stderr, "server: failed to bind\n");
    exit(1);
}

if (listen(sockfd, BACKLOG) == -1) {
    perror("listen");
    exit(1);
}

sa.sa_handler = sigchld_handler; // reap all dead processes
sigemptyset(&amp;sa.sa_mask);
sa.sa_flags = SA_RESTART;
if (sigaction(SIGCHLD, &amp;sa, NULL) == -1) {
    perror("sigaction");
    exit(1);
}

printf("server: waiting for connections...\n");

while(1) {  // main accept() loop
    sin_size = sizeof their_addr;
    new_fd = accept(sockfd, (struct sockaddr *)&amp;their_addr, &amp;sin_size);
    if (new_fd == -1) {
        perror("accept");
        continue;
    }

    inet_ntop(their_addr.ss_family,
        get_in_addr((struct sockaddr *)&amp;their_addr),
        s, sizeof s);
    printf("server: got connection from %s\n", s);

    if (!fork()) { // this is the child process
        close(sockfd); // child doesn't need the listener
        if (send(new_fd, "Hello, world!", 13, 0) == -1)
            perror("send");
        if (numbytes = recv(new_fd, &amp;buf, MAXDATASIZE-1, 0) == -1) {
            perror("recv");
            exit(1);
        } 

        buf[numbytes] = '\0';
        printf("server: received '%s'\n",buf);
        close(new_fd);
        exit(0);
    }
    close(new_fd);  // parent doesn't need this
}

return 0;
}
</code></pre>
