client.cpp

#include <iostream>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>

using namespace std;

int main(int argc, char** argv)
{
    sockaddr_in server;
    int sock;
    char buf[32];
    char *deststr;
    int n;

    if (argc != 2) {
        cout << "Usage : " << argv[0] << " dest" << endl;
        return 1;
    }
    deststr = argv[1];

    sock = socket(AF_INET, SOCK_STREAM, 0);

    memset(&server, 0, sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(8080);

    //server.sin_addr.s_addr = inet_addr(deststr);
    server.sin_addr.s_addr = inet_addr("127.0.0.1");
    //if (server.sin_addr.s_addr == 0xffffffff) {
    //    hostent *host;
    //    host = gethostbyname(deststr);
    //    if (host == NULL) {
    //        return 1;
    //    }
    //    server.sin_addr.s_addr = *(unsigned int *)host->h_addr_list[0];
    //}
    connect(sock, (sockaddr *)&server, sizeof(server));

    memset(buf, 0, sizeof(buf));
    cout << "reading from server" << endl;
    n = read(sock, buf, sizeof(buf) - 1);

    cout << n << ' ' << buf << endl;

    close(sock);

    return 0;
}

echo.cpp

#include <iostream>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>

using namespace std;

int main()
{
    int sock0;
    sockaddr_in addr, client;
    socklen_t len;
    int sock;

    sock0 = socket(AF_INET, SOCK_STREAM, 0);
    cout << "echo sock0 = " << sock0 << endl;

    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8080);
    addr.sin_addr.s_addr = INADDR_ANY;
    addr.sin_len = sizeof(addr);

    bind(sock0, (sockaddr *)&addr, sizeof(addr));

    listen(sock0, 5);

    while (1) {
        len = sizeof(client);
        cout << "accepting client" << endl;
        sock = accept(sock0, (sockaddr *)&client, &len);
        cout << "writing to client" << endl;
        write(sock, "Hello", 5);

        close(sock);
    }

    close(sock0);

    return 0;
}